Voice Responses are contextually triggered lines that play after the player has achieved something, for instance killing a certain amount of enemies with a Primary or Melee Weapon, or the player has triggered something, like being set on fire. The Engineer has several voice responses, all of which are listed below (excluding Voice Commands).
Kill-related responses
Domination-related responses
Event-related responses
Objective-related responses
Setup/Between Waves
During a Wave
After a Wave
Duel-related responses