From Halopedia, the Halo wiki
Singleplayer: Meeting the Flood for the first time; "Objective: SURVIVE" Multiplayer: Being the Last Man Standing three Infection games in a row and racking up 25 kills in one round; going into a game of SWAT as a low rank and completely spanking the trash-talkers on the other team.
Playing any sort of Juggernaut game where I do not immediately spawn as the Juggernaut. Seriously, all I ever get are assists. Nothing else. Games of Big Team Snipers are also pretty awful as well.
Favorite Game Modes: Rumble Pit: Infection
Rumble Pit: Slayer Pro
Team Slayer: SWAT
Invasion: Boneyard Invasion
Oh, and anything in Forgeworld. What a fun map!