Halo 3

Trivia: In Crow's Nest, on different difficulties, you are able to hear different voice actors from Rooster Teeth arguing about the apparent "password" to a door in the main hallway. The voices will reflect the Red vs. Blue character's personality that each specific actor plays and refer to things that happen to that character in the series (eg. Church getting pissed at Caboose for being a total moron, Grif and staff meetings/ammunition). Killing the knocker will end the conversation regardless of who is speaking at that time.