Item sets

Item sets is a game concept introduced in the Mann-Conomy Update, which applies new attributes (such as greater damage resistance, immunity from headshots, etc.) to the wearer when all items in the set are equipped. There are currently five items sets, all of which are from the Polycount Pack.

Since Valve is of the opinion that game-changing effects should be available for every player within a reasonable amount of time, these hats are the only hats in the game to have guaranteed blueprints for crafting besides the Bonk Helm, requiring four Refined Metal and any Polycount Pack Weapon from the class you want to craft the hat for.

The Scout

Main article: Item sets

The Special Delivery
	Shortstop Mad Milk Holy Mackerel Milkman
Effect	Leave a Calling Card on your victims

The Soldier

Main article: Item sets

The Tank Buster
	Black Box Battalion's Backup Grenadier's Softcap
Effect	Leave a Calling Card on your victims

Obviously an excellent class set focused on Sentries.

The Black Box is, like the Milk, a great weapon to go around without the need of a Medic. The Backup is good when you need to get people across the range of a Sentry, but a Medic helps as they are not totally invincible.

On a side note, the Rocket Jumper is nice to practice getting around the map fast and effectively, but as mentioned before, it's not a great idea to use in combat.