User:Toomai/MvM strategy overhaul

I think Community Mann vs. Machine strategy could do with a split into "strats for players" and "strats against bots". This'll be the former.

Colours for reference (from paint, like mission tables):

Essential	The average MvM player will expect to see this in their teammates' loadout, and for good reason.
Recommended	A generally-preferred option that nevertheless has some weaknesses.
Average	Has pros and cons, or might simply have an underdeveloped meta.
Discouraged	A pro could probably make this work, but there are better options.
Worthless	For whatever reason, this has no practical use in the mode.

 Scout

Loadout

Primary
Scattergun	You can never go wrong with the stock Scattergun.
Force-A-Nature	Cheaper to upgrade to reach higher damage potential, and knockback is helpful to control robots, but your teammates may not appreciate it if you make robots bounce around every time you shoot them.
Shortstop	Effective at longer ranges and has good maximum damage rate, but is more expensive to upgrade.
Soda Popper	Cheaper to upgrade to reach higher damage potential and also unlocks additional mobility through Hype.
Baby Face's Blaster	Against hordes of robots, it becomes quite easy to build the weapon's Boost meter. However, it has the lowest damage potential of all the Scout's primaries, and upgrading movement speed already brings the Scout to near the game's running speed cap.
Back Scatter	Being able to mini-crit giants from behind can be useful, but there are several better ways to achieve mini-crits, and the weapon is otherwise outclassed by the other options.
Secondary
Pistols	In essentially all situations, it is more effective to simply reload the Scout's primary weapon than to switch to his less-damaging secondary one, especially once reload speed has been upgraded. Using a pistol for its higher long-range damage is also simply subpar, as it's not worth upgrading.
Bonk! Atomic Punch	The invincibility that Bonk! provides makes it possible to collect dangerously-placed credits safely, but it is generally inferior to Über Canteens, as it renders the Scout unable to attack for a sizeable amount of time.
Crit-a-Cola	The extra damage provided by Crit-a-Cola is not a bad option for a purely-offensive Scout. Compared to the Fan O'War, it can deal mini-crits to several enemies at once, but cannot do so for teammates.
Mad Milk	Mad Milk is an exceptional team support tool, allowing teammates to heal by attacking sodden enemies, and a single inexpensive upgrade makes bots easier to hit and cripples Giant Scouts' ability to tear through the team's defenses.
Flying Guillotine	Designed to destroy singled-out, stunned targets, the Flying Guillotine has poor utility against a horde of robots.
Melee
Stock	The Bat and Holy Mackerel do not have any positive attributes to take advantage of, making them unsuitable for MvM compared to the alternatives.
Sandman	The ability to mark giants for death at long range is useful, but the upgrade required to do so is expensive, in addition to requiring ammo. The Sandman also reduces the Scout's max health significantly, which while not much of an issue after collecting a lot of credits, will be a concern at the start of each wave.
Boston Basher	While there is minor utility in helping your Medic build ÜberCharge or revealing Spies, time spent smacking robots to make them bleed would be better spent simply killing them with your primary weapon.
Candy Cane	A good Scout should be overhealed at all times from collecting credits, and the health kits that drop from killed robots will be in the line of fire more often than not, making them risky for teammates to go for. The Candy Cane is a good source of afterburn control if there are a lot of enemy Pyros, but the substantial increase in explosive damage is costly.
Sun-on-a-Stick	The Scout has higher damage-per-second with non-upgraded primary weapons than using this weapon on burning enemies. Its only potential use is against Heavies with the Fists of Steel, and even then this requires a Pyro on the team.
Fan O'War	One hit from this weapon marks giant robots for mini-crits for 7.5 seconds, effectively cutting their maximum health by 25% if it is constantly re-applied. With no upgrades required, it is one of the most effective ways to accelerate the takedown of stubborn robots.
Atomizer	A single extra jump is negligible in the grand scheme of things, especially if the Scout has the Soda Popper or jump height upgrades.
Wrap Assassin	Bleeding is a generally ineffective means of damage, and the weapon is basically incapable of killing enemies straight-up, making it a poor choice overall.

Upgrades

Personal
Resistances	It is important for a Scout to shrug off damage before he can get his health supercharged by money at the start of waves, and it is even more useful to maintain such overheal levels.
Mobility	Movement speed and jump height are useful to not only dodge enemy fire, but get around the map to collect all the credits. It is potentially overkill to maximize these upgrades, as moving too fast or jumping too high can make it difficult to actually attack enemies.
Regeneration	This upgrade has no use for a Scout that remains at full health or above by collecting credits, which he should be doing.
Primary
Damage output	Upping damage dealt helps immensely with killing Medics in one shot and destroying Tanks.
Penetration	Since the Scout's primary weapons deal the most damage at point-blank, robot crowds must be extremely thick to get much more than chip damage beyond the frontmost target. Situational as a result.
Ammo	One of the Scout's main weaknesses is an inability to keep fights sustained due to lacking clip and ammo. Upgrading these attributes plus reload speed makes him even more of a damage-dealer.
Health on kill	Scouts effectively already have health-on-kill via credits, so it's a bit of a waste to upgrade.
Secondary
Pistols	Even for Scouts that are using a pistol, quite a lot of money must be spent here for any notable effect.
Bonk!	If you're going with a soda can, this is all that's available, so might as well use it.
Mad Milk	The snaring effect of upgraded Mad Milk is cheap and powerful. Recharge speed can be help but is less necessary.
Melee
Offensive	Scouts generally should not be using melee weapons on robots as a killing tactic.
Projectile	If a Scout has indeed chosen to use the Sandman, these upgrades are highly useful.
Canteen
Über	A few seconds of invincibility can give a Scout just enough time to take down a robot and heal from the money it drops, wade through heavy fire to collect credits in a dangerous spot, or simply distract enemies to buy time for teammates.
Kritz	Scouts are already exceptional at killing Tanks, and having crits multiplies his effectiveness even further. It also makes it safer for him to go after Medics, making it easier to kill them in one shot and avoid having them use their charge.
Ammo	Most Scouts should have enough time while they're reloading or between sub-waves to dash to an ammo pick-up or the team's Dispenser.
Return	If a Giant Scout slips through the defense, having a Scout teleport back may be the team's best chance of catching them quickly. However, this is rather situational, and a Scout should be able to catch any other loose robot on his own.

 Soldier

Loadout

Primary
Rocket Launcher	You can never go wrong with the stock Rocket Launcher.
Direct Hit	Giant robots and tanks are easy targets for the Direct Hit's higher damage, but they cannot be juggled, and splash damage is very important to take out several robots at once.
Black Box	The loss of one rocket is not hard to compensate for with upgrades, and hitting several robots at once will keep your health decently full.
Rocket Jumper	For obvious reasons, this item should not be used.
Liberty Launcher	The Libery Launcher's lower damage output is a major problem that is not truly compensated for by its upsides.
Cow Mangler 5000	With infinite ammo, the Cow Mangler is cheaper to upgrade than other rocket launchers. However, the lack of critical hits is a significant downside that the entire team may have to compensate for.
Original	Most MvM maps prioritize height advantage over peeking around corners, so this weapon is not much different than the stock.
Beggar's Bazooka	With a horde of robots to fire at, this weapon's only downside is negated - there's so much stuff to hit that only distant Snipers will result in missing. With upgraded reload speed, the Soldier can fire single rockets at high speed, or quickly load up a barrage to fire all at once just after activating a Kritz canteen.
Air Strike	Poor in early-game with its reduced splash and damage, but in late-game, raining 16-rocket barrages from above can be devastating.
Secondary
Shotguns	Carrying a sidearm, which really only has a use when out of rockets, is simply inferior to carrying a team-boosting banner.
Boots	These items have no value when defending against an invading robot horde.
Buff Banner	Deploying mini-crits to anyone nearby is an invaluable tool in a mode based on dealing high amounts of damage. Use the banner as often as possible as opposed to saving it for specific moments, to increase the number of times it gets deployed.
Battalion's Backup	Depending on team composition and the presence of crit-boosted robots, this banner can be a better choice than the Buff Banner.
Concheror	Being able to keep the whole team healed is a decent ability, and the mobility boost helps positioning and money collection.
Righteous Bison	The Bison is cheap to upgrade and naturally penetrates through unlimited numbers of robots, but it is difficult to recommend over a team-boosting banner.
B.A.S.E. Jumper	Only really useful in conjunction with the Air Strike, and even then it deprives the player of a team support tool.
Melee
Shovel	The Soldier has far better melee weapons to choose from.
Equalizer	A weakened Soldier will be doing high damage with each melee swing, but this is naturally risky.
Pain Train	With no points to capture, this weapon has no upside.
Half-Zatoichi	As long as the Soldier can land the last hit on an enemy, this will refill his health in an instant, making it a decent choice when surrounded.
Disciplinary Action	Aside from its speed-boosting ability, the weapon's ridiculous melee range helps in attacking Steel Gauntlets at a safe distance.
Market Gardener	In a mode with many foes at once, taking out one at a time with a rocket jump in between is very inefficient.
Escape Plan	A good retreating tool, though crit resistance might need to be applied for best usage.

Upgrades

Personal
Resistances	Blast resistance reduces damage taken from rocket jumping, making it a good choice even for Soldiers that are otherwise not investing in resistances.
Mobility	Rocket jumping mostly overshadows any usage that mobility upgrades can provide.
Regeneration	The health loss from rocket jumping, fall damage, and close-range fighting can add up quickly. Having free health regeneration can help offset this quite well.
Primary
Rocket specialist	Most Soldiers should try to put at least one point into this upgrade, as it will allow direct hits to override distance falloff in addition to stunning the target. Soldiers may or may not want to buy any more depending on how well they can tolerate the rocket speed modification.
Damage output	High damage output is the Soldier's main job, and will help charge his banner faster.
Ammo	Reload and firing speed are the most important upgrades to buy, as they offset the Soldier's arguably-main weakness. Ammo capacity is less universally-helpful but still very useful.
Health on kill	Soldiers should be racking up a lot of cleanup kills, so this is not a bad idea to get.
Secondary
Sidearms	Even for Soldiers that are using a shotgun or the Bison, quite a lot of money must be spent here for any notable effect.
Banners	It is usually more efficient to have longer-lasting buffs as opposed to building, using, and rebuilding multiple shorter buffs.
Melee
	Soldiers who wish to get health from killing robots should probably be using the Half-Zatoichi as opposed to buying the related upgrade, and melee attack speed only really has a use when fresh out of rockets.
Canteen
Über	There's nothing wrong with temporary invincibiliy, but most of the time a Soldier can simply rocket jump away from bad situations.
Kritz	Crit rockets are a Soldier's best weapon in MvM. Use them liberally.
Ammo	There is situational use in an instant clip refill.
Return	Soldiers should be capable of catching up to bots without teleporting.

 Pyro

Loadout

Primary
Flame Thrower	You can never go wrong with the stock flamethrower.
Backburner	Crits from behind are devastating to giant robots, which take a while to turn around, but the costlier airblast will have to be compensated for by either more ammo upgrades or a teammate.
Degreaser	The typical MvM Pyro should be in the fray at all times without need to switch weapons quickly, and the Degreaser is also the Pyro's worst damage-dealer in both raw damage and afterburn.
Phlogistinator	With so many robots to burn, a Phlog Pyro should have crits and healing on demand at almost all times. However, the inability to airblast cannot be overstated.
Secondary
Shotguns	Only if a Pyro runs out of ammo would he ever need to switch to a shotgun, a situation that he shouldn't be getting into anyways.
Flare Gun	Shooting flares at Snipers is a decent way of distracting them, or outright killing them if they remain still for a second shot. It is also good for dealing damage to Giants while walking up to them.
Detonator	Similar to the Flare Gun, though with less damage and more mobility.
Manmelter	Gaining crits via extinguishing teammates is very situational, and other flare secondaries tend to result in more damage for less effort.
Scorch Shot	Acts like a long-range airblast to knock back distant robots, but with not much else.
Melee
Fire Axe	The Pyro has far better melee weapons to choose from.
Axtinguisher	A reliable way to delete Über Medics, but poor for most other situations.
Homewrecker	Worthless against robots, but gets rid of enemy Sappers, which can be a lifesaver if the Engineer is killed before he can unsap his buildings.
Powerjack	Extra speed and health are helpful, but landing the final strike on an enemy can be difficult.
Back Scratcher	In early waves, getting additional health from health packs can be a major source of survival, and even once health-based upgrades and resistances are bought, it still does additional damage. However, the team's Medic and Dispenser become near-worthless to you.
Sharpened Volcano Fragment	With afterburn being unreliable overall, the weapon's lower damage doesn't really jive with the Pyro's playstyle.
Third Degree	While this weapon can eradicate all the Medics off a giant with a single crit swing, it needs three non-crit swings to do so, the second one probably causing them to pop their charge.
Neon Annihilator	There are better ways to kill enemies than to depend on a teammate to soak them.

Upgrades

Personal
Resistances	As Pyros should be spending all their time in close range, being able to resist most of the damage coming their way is essential to remain alive.
Mobility	It is important for a Pyro to get into close range to attack yet also get out if things get to dangerous.
Regeneration	It is difficult to say whether health regeneration is good for Pyros - any source of health is appreciated, and depending on team composition and skill the Pyro might be dealing lots of damage without actually scoring many kills, but regeneration only works of the player is not overhealed from a Medic or health-on-kill.
Primary
Raw damage	Pure damage is the Pyro's main goal, especially against Tanks.
Afterburn	Fully-upgraded afterburn can do a maximum of 240 damage after a total of 20 seconds. This sounds high, but a Pyro can use money on raw damage instead to reach over 300 damage per second and have some cash left over. Afterburn upgrades are simply not worth the cost.
Ammo	For Pyros that don't want to have to leave the fight to forage for ammo, and especially for Backburners trying to airblast robots, this is very useful.
Health on kill	Pyros in the fray should be collecting a lot of cleanup kills, so using them to keep health high is super-helpful.
Airblast force	The majority of robots are easy enough to push around with no money invested here, and the majority of giants have too much knockback resistance for this to matter. Its main use is to throw robots into a setback ditch or deathpit with fewer airblasts necessary, making this almost act like an ammo upgrade.
Secondary
Shotguns	Why are you using a shotgun again?
Flare guns	Pyros should not be spending enough time at long range for these upgrades to matter.
Melee
	Some of the Pyro's weapons can benefit from faster swing speed, but overall the money is probably better spent elsewhere.
Canteen
Über	As Pyros thrive in close range, invincibility is a major boon for when things go south.
Kritz	Not a bad option for destroying Tanks and giants.
Ammo	Pyros that don't wish to leave the fight to find ammo may opt for this.
Return	The ability to catch up to a robot and airblast them back makes Pyro one of the better users of this canteen.

 Demoman

Loadout

Primary
Grenade Launcher	You can never go wrong with the stock Grenade Launcher.
Loch-n-Load	Very much a sidegrade compared to the stock, with its higher damage being counterbalanced by its smaller explosions and direct-hit requirements.
Ali Baba's Wee Booties	Demoknights, or Demomen exclusively focused on their stickies, can find reason to give up grenades for a substantial health boost.
Loose Cannon	The knockback of cannonballs is good for controlling robots' movements, but the weapon deals less damage overall, especially to tanks.
B.A.S.E. Jumper	Unlike the Solider, the Demoman has little reason to hang vulnerable in the sky for long periods of time.
Iron Bomber	Lower explosive radius, lower damage on miss, and no real upside leaves this weapon in a poor spot.
Secondary
Stickybomb Launcher	You can never go wrong with the stock Stickybomb Launcher.
Chargin' Targe	The preferred Demoknight shield, as it has the best resistances (including complete afterburn immunity), and having Crits On Kill for melee weapons is more effective than charging.
Scottish Resistance	The slower arm time is mostly irrelevant given the robots' predictable movement, and having 6 more stickies active at a time that can be detonated individually grants much more power to sticky traps.
Sticky Jumper	For obvious reasons, this weapon should not be used.
Splendid Screen	Shield bashes, this weapon's speciality, are extremely inefficient at damaging robots.
Tide Turner	Demoknights do not need to charge that often in MvM, and the weapon's "damage shortens charges" weakness can be crippling.
Quickiebomb Launcher	The lack of sticky traps is not quite made up for by stronger straight-up damage capabilities.
Melee
Bottle	The Bottle has no upsides to exploit or downsides to tolerate.
Eyelander	While a Demoman with the Eyelander is weaker to start, after a few melee kills, he has much improved speed and health. It works well for any Demoknight, while for a Demoman with stickies, it is riskier.
Pain Train	With no points to capture, this weapon has no upside.
Scotsman's Skullcutter	Having longer range with more damage is countered by slower movement speed. For Demos that are not intenting to fight at close range much, this is a good choice for when Steel Gauntlets appear.
Ullapool Caber	With no resupply cabinets in MvM maps, this weapon's one-shot nature makes it very difficult to recommend.
Claidheamh Mòr	Most MvM maps don't have enough space for longer charges to reach full potential.
Half-Zatoichi	On a Demoknight with no other weapons to switch to, this can easily make him extremely bulky.
Persian Persuader	While charges aren't as useful as in other game modes, having one available for escape can be useful. Non-Demoknights should never use this, as ammo is scarce enough in most MvM maps.

Upgrades

Personal
Resistances	Even if a Demoman isn't investing too much into resistances, explosive resistance makes sticky jumping and close-range detonations safer. Resistances in general are highly useful for Demoknights, stacking with whatever their shield has.
Mobility	Demoman has slightly below-average mobility with no real need to move around quickly, while Demoknights have shield charges available. Therefore, upgrading mobility is not essential.
Regeneration	Having a way to offset self-damage taken is a strong reason to buy this.
Primary
Raw damage	The higher cost for less effect on both the Demo's explosive weapon slots makes it prohibitively expensive to upgrade both weapons at once. Demos focused on grenades may find upgrading direct damage to be not worth the cost compared to other attributes.
Speed and ammo	If grenades are the weapon of choice, all these upgrades are highly useful.
Projectile speed	While this effectively increases the range of grenades, it can easily throw off players' aim and has no additional properties like the Soldier's version.
Health on kill	Any way of restoring health is welcome, though depending on your loadout and the team you may find yourself dealing a lot of damage without a lot of kills.
Secondary
Raw damage	The higher cost for less effect on both the Demo's explosive weapon slots makes it prohibitively expensive to upgrade both weapons at once. Demos focused on stickies can use higher damage to spread their traps farther out for equal damage, or keep them concentrated for even more damage on fewer targets.
Speed and ammo	If stickies are the weapon of choice, all these upgrades are highly useful.
Health on kill	Depending on your weapon and playstyle, kills with stickies may be either common enough for this to be worthwhile or rare enough that this is not helpful.
Demoknight	Charging more often is more of a bonus than a necessary skill to have in MvM. Taking reduced knockback is a highly-situational upgrade that may not see any use when not facing dedicated pusher robots.
Melee
Demoman	It will probably be more effective overall for a Demoman to invest in explosive resistance and just blow things up at short range rather than switch to his weaker melee weapon.
Demoknight	This is where a Demoknight should be spending most of his money, allowing him to get a single kill with a shield charge and go on a rapid-fire rampage of chained critical sword swings, overhealing him the whole time.
Canteen
Über	There's nothing wrong with temporary invincibility, especially when trying to fight at close range.
Kritz	Crit explosives are immensely useful in MvM, and if the team doesn't have a Medic, this is the best way at using them.
Ammo	There is situational use in an instant clip refill.
Return	Being able to teleport ahead of a slippery bot and lay down a sticky carpet for it is probably one of the better usages of this canteen.

 Heavy

Loadout

Primary
Minigun	You can never go wrong with Sasha.
Natascha	More ammo to spare and the ability to slow enemies while damaging them are extremely useful in certain waves, especially against Giant Scouts. However, the lower damage is quite noticable on already-slow robots.
Brass Beast	While this weapon's higher damage is very appealing, its extremely high mobility cost can be a major issue if Snipers are present.
Tomislav	The Tomislav's slower firing rate adds up quickly, and robots do not hear deployed miniguns anyway.
Huo-Long Heater	Minigun ammo can already be a problem for Heavies, and since afterburn is weak overall, cannot be upgraded, and Spies are both rare and announced, there is not much upside to this weapon.
Secondary
Shotguns	Most of a Heavy's time and money should be spent on his minigun; switching to a shotgun is not really any faster than spinning up, and there are better ways to deal with ammo issues.
Sandvich	Providing a free medium healthkit to teammates and a full heal to himself with unoccupied, the Sandvich is highly useful even if the team has a Medic.
Dalokohs Bar	In addition to being rendered useless by simply having a Medic, the 50 extra HP this item grants is outclassed by just buying a resistance upgrade, which acts an effective 75 HP boost.
Buffalo Steak Sandvich	The Heavy's main draw in MvM is his minigun; he should not be putting it away to punch robots while taking increased damage.
Melee
Fists	Pow!
Killing Gloves of Boxing	It is usually quite risky for a Heavy to try and land a finishing punch on an enemy, but being able to do so effectively grants him a free Kritz Canteen. Best used with a minigun of stock or reduced spin-up time.
Gloves of Running Urgently	As Heavies generally should not be getting into melee combat, the GRU's running speed boost is a good way to help him move about the field. Upgrading crit resistance helps offset the only remaining downside.
Warrior's Spirit	Reducing max health while encouraging melee combat is not a promising combination.
Fists of Steel	Steel Gauntlets use this item because their goal is to stay alive, not to kill enemies. As the Heavy himself is in somewhat of the reverse situation, he finds less use for it.
Eviction Notice	Faster punching speed doesn't mean much when the DPS is lower overall.
Holiday Punch	Robots contain (repaired) Humor Supression Pumps. Attempting to get them to laugh is futile.
Canteen
Über	A burst of guaranteed survival is quite a useful tool for Heavies.
Kritz	Having crits on demand is a powerful tool.
Ammo	Ammo can be a problem for Heavies, so having an instant refill is very useful.
Return	With the slowest running speed and the need to spin up his minigun, it's impractical at best for a Heavy to be the one chasing down stragglers.

 Engineer

Loadout

Primary
Shotgun	You can never go wrong with the stock Shotgun.
Frontier Justice	With the amount of kills and assists the typical Engineer should be racking up, the Frontier Justice is a source of almost limitless crits once the first Sentry is destroyed. Engineers with this weapon should prioritize staying alive and make sure to destroy their Sentry between waves (or even allow Sentry Busters to do so during waves) to unlock the crits.
Widowmaker	Since it uses Metal for ammo, the Widowmaker is very cheap to upgrade, requires no reloading, and in the hands of a decent shot will keep you constantly filled with Metal. With piercing bullets and max metal upgrades, the weapon can become a source of unlimited harrassment and distraction.
Pomson 6000	While not very useful against most robots, the Pomson excels at weakening Medics and Spies, giving the team a wider window of opportunity to destroy them.
Rescue Ranger	The ability to heal and haul buildings at long range less Engineers place high-level Sentries as distractions and cart them off to safe havens when their health gets low, or quickly teleport them back and forth across an area. However, as Engineers do not run slower while hauling in MvM, it is not as useful for moving up a base as in other modes, and being marked for death can be a serious problem if your nest is swarmed.
Panic Attack	It is risky for an Engineer to rely on this weapon, as he cannot switch weapons while loading or firing it, which can leave his buildings open if he can't switch back to his wrench in time.
Secondary
Pistol	While there's nothing inherently wrong with the Pistol, it is simply outclassed by the Engineer's other options unless he is going full Gunslinger.
Wrangler	The Wrangler allows Engineers to intelligently prioritize targets, raise their Sentry's DPS for taking down giants and tanks, absorb tons of damage when combined with building health upgrades, and fire back at distant Snipers or Spies. Its only downside is that activating it can allow Scouts to slip though the front lines.
Short Circuit	The ability to wipe out entire volleys of projectiles is very powerful, but at a steep Metal cost that cannot be easily replenished without switching away from the weapon. In addition, Heavies and Medics have more effective tools for projectile control, even though they have to buy them.
Melee
Wrench	You can never go wrong with the stock Wrench.
Gunslinger	Mini-Sentries are cheap and fast, the health boost allows the Engineer to dive into the fight himself more, and punching crits can be effective against giants. However, giving up level 3 sentries is not a choice to be made lightly, and the team will need to prepare itself accordingly before the first wave begins.
Southern Hospitality	Engineers should not be attacking robots directly with their wrench outside a last resort, meaning this weapon has no upside.
Jag	Since the Jag's only downside is less melee damage, it's a good choice for Engineers that wish to forego Upgrade canteens.
Eureka Effect	The Eureka Effect's taunt acts as an Ammo canteen and Return canteen at once, in addition to fully healing him, a rare luxury in MvM maps. However, its lower repair and upgrade speeds can easily cripple a Sentry under fire, requiring swing speed upgrades to keep pace. In addition, the process of using its teleport is quite long, making it hard to use when under fire.
Canteen
Über	There are better ways of dealing with Sentry Busters than by Übering the Engineer and Sentry.
Kritz	Additional Sentry firing speed is probably better off left to the Wrangler than a canteen.
Ammo	An instant Metal refill can be a lifesaver in some situations, especially in conjunction with the Widowmaker or Short Circuit.
Return	Being able to haul a level 3 Sentry to the base in an instant is a useful tool, but often the same thing can be accomplished by building a two-way teleporter.
Upgrade	The ability to put up a level 3 Sentry and Dispenser in an instant cannot be understand, especially when there is no time to rebuild manually during a wave.

 Medic

Loadout

Primary
Syringe Gun	The stock Syringe Gun has no upsides to work with or downsides to avoid.
Blutsauger	Unless the Medic is actually fighting with this weapon (and therefore not healing his team as much), he is hampering his self-regeneration with it.
Crusader's Crossbow	With the ability to heal teammates at long range and deal surprisingly high damage to distant Snipers, the Crossbow is quite useful in many situations.
Overdose	A minor damage reduction conbimed with a minor speed increase equals out to an average option.
Secondary
Medi Gun	Invulnerability is a strong tool against the robot horde, allowing a patient (or two) to survive literally anything while spitting out damage. However, out of all the Medic's options, it takes the longest to build up.
Kritzkrieg	As dealing high amounts of damage is the main goal of the mode, having command of guaranteed crits is a godsend to any class it's trained upon. It allows Demos to spread out critical carpets of stickies before the wave begins, Soldiers to fire walls of crit rockets at the oncoming horde, or Pyros to melt the sides off a Tank. It also allows the Medic to spend his money on the cheaper canteens to share.
Quick-Fix	With its higher healing rate, the Quick-Fix can charge its projectile shield and revive teammates faster, and the knockback immuniy its Megaheal provides can help against pusher robots. However, its charge is otherwise quite weak, and its lower overheal can be a problem if not upgraded to compensate.
Vaccinator	When used properly, the Vaccinator can render both the Medic and his patient completely immune to crits and almost immune to whatever else is incoming. Its main drawback is the higher learning curve required to tap into its versatility.
Melee
Bonesaw	The stock Bonesaw has no attributes, useful or otherwise.
Ubersaw	It is risky for a Medic to poke a robot with his melee weapon to acquire über, but simply carrying the weapon in case an opportunity presents itself (such as stunned or sapped robots) is never a bad idea.
Vita-Saw	Comapred to regular multiplayer, the balance in MvM of "stay alive" versus "rebuild time after death" is skewed much more heavily towards survival, making the Vita-Saw's max health reduction a much larger disadvantage (especially once charge speed is upgraded).
Amputator	The Medicating Melody and higher regeneration rate are good reason to choose the Amputator, as its downside in damage is not really relevant.
Solemn Vow	All players can see the health of giant robots and Tanks at all times, so even though this weapon is a straight upgrade over the stock Bonesaw, it is equally useless.
Canteen
Über	A solid choice for Kritzkrieg users, allowing the Medic to dispense both crits and invincibility.
Kritz	When not using the Kritzkrieg, this lets the Medic pop crits on patients anyway for short bursts of high damage.
Ammo	With proper team communication, a Medic can use an Ammo canteen to double the size of his patient's clip during a Kritzkrieg, Buff Banner, or patient's Kritz canteen. Without proper communication, the patient may buy Ammo canteens of their own or break off their attack preparing to reload.
Return	Medics cannot share this canteen, so if a robot sneaks through to the base, they will have to take them out alone with weapons that are likely not upgraded.

 Sniper

Loadout

Primary
Sniper Rifle	You can never go wrong with the stock Sniper Rifle.
Huntsman	Without explosive headshots, a Huntsman Sniper loses an effective manner of crowd control, which cannot reasonably be made up for with the bleeding upgrade.
Sydney Sleeper	Applying Jarate at long range is a useful tool, but its lack of headshots is a major downgrade. Note that the Sydney Sleeper can still apply explosive headshots.
Bazaar Bargain	The effectiveness of this weapon is directly linked to the skill of the user. In the hands of a headshotting pro, it charges extremely fast; in the hands of a novice, it is of little value.
Machina	The downsides of the Machina are minimal compared to its higher damage and built-in penetration when fully charged.
Hitman's Heatmaker	The Heatmaker's Focus ability allows the Sniper to rapid-fire partially charged heatshots, and with so many robots to kill, it is possible to remain scoped almost indefinitely.
Classic	The inability to deal headshot damage when not fully charged is difficult to work around, but being able to do so without being scoped can help keep an eye on other threats.
Secondary
SMG	The SMG's only use is for personal defense when attacked up close.
Jarate	An incredibly useful tool for any team, Jarate not only applies mini-crits to multiple enemies at once, but with a single cheap upgrade, it also slows them down and renders them unable to slip through the team's defenses.
Razorback	With no resupply lockers in MvM maps, and occasional bugs that allow Spy Robots to circumvent the item, the Razorback has very poor situational use.
Darwin's Danger Shield	Extra health and bullet resistance is helpful, but the higher explosive weakness and lack of a secondary weapon make this item less than ideal.
Cozy Camper	Free health regeneration is nice, but the flinching immunity is situational, as robots tend to not fire at Snipers until they are decently close anyway.
Cleaner's Carbine	Snipers that wish to fight on the front lines can find the Carbine a useful source of mini-crits, but this requires him to land the final hit in an enemy (which is challenging with five other teammates shooting at the same targets), and the weapon's slower firing speed is expensive to offset.
Melee
Kukri	A stock melee weapon with no upsides to exploit or downsides to avoid.
Tribalman's Shiv	A Sniper in melee combat is probably trying to save his own skin rather than trying to go on the offensive against bulky robots, and bleeding is more often than not a poor source of damage.
Bushwacka	With several ways to gain mini-crits, such as Jarate or a teammate's Buff Banner, the Bushwacka's ability to turn them into full crits is exceptionally useful against oblivious giants and tanks.
Shahanshah	Using a melee weapon as a Sniper is probably a last resort, so having hgiher damage when injured is not that bad.
Canteen
Über	Snipers have little use for invincibility unless they are overwhelmed, in which case they probably won't be able to survive regardless.
Kritz	The ability to rapid-fire headshot damage without scoping is good in a pinch.
Ammo	Most Snipers shouldn't be running through ammo fast enough to require refilling while busy, and many sniping spots have ammo pickups available.
Return	If a robot gets through the defense, a Sniper might not be able to do much to stop it even if he heads it off.

 Spy

Loadout

Primary
Revolver
Ambassador	With less damage and a focus on headshots, no upgrades that take advantage of headshots, and a mantadory cooldown period, the Ambassador is not exceptionally useful against a horde of robots.
L'Etranger	Spies are not expected to contribute ranged damage anyway, so L'Etranger's lower damage is not much of a downside. On the other hand, it allows cloak to be charged faster and used more, allowing the Spy to position himself better.
Enforcer	If a Spy is shooting something, it is probably a Tank, making disguising useless and this weapon a good choice.
Diamondback	While it does slightly less damage, the ability to store many crits via backstabs allows the Spy to do appreciable damage to faraway enemies and Tanks.
Secondary
Sapper	There is nothing exceptional about the Sapper.
Red-Tape Recorder	There is no functional difference between the two sapper options when used on robots. Against enemy buildings, the Red-Tape Recorder can delevel buildings, but leaves them around for potential saving for longer.
Melee
Knife	You can never go wrong with the stock Knife.
Your Eternal Reward	The specifics of robots' spy-detection mechanics result in this weapon being functionally useless.
Conniver's Kunai	The initial health penalty is a major issue, but the Kunai eliminates the need for health-on-kill upgrades.
Big Earner	With not-as-drastic health reduction, the Big Earner makes it very easy to keep cloak fully charged.
Spy-cicle	Being without a knife, the Spy's primary weapon in MvM, for 15 whole seconds, is a major drawback that does not quite compensate for 2 seconds of fire immunity.
Watch
Invis Watch	Ammo tends to be scarce on MvM maps, so refilling cloak can be an issue.
Cloak and Dagger	This watch is suited for slow or stationary espionage, which does not jive well with the mode's mechanics.
Dead Ringer	Robots are always completely fooled by feigned deaths unless the Spy catches on fire, and they ignore decloacking noises. As long as the Spy can keep his cloak fully charged, he can use the Dead Ringer to escape from almost any situation and come back for more.
Canteen
Über	Having a safety net in case of discovery can be useful.
Kritz	The Spy has poor damage output overall, and would probably be better off with a cheaper canteen.
Ammo	Sappers are essential to slow down fast robots, and having a freebie at your disposal can be a game-changer.
Return	If a fast robot gets through with the bomb, a Spy can teleport to the base and sap-n-stab them.