I really hate it when you are trying to be stealthy/quiet because the enemy is around and all of the sudden the guy next to you is like "Oh man that was a awesome game on Halo last night! We ownzord leet 2cool4school haxor nerd ed those guys!" And they dont even whisper!
What I do like is being the last guy alive and have the adreniline (sp) rush of being hunted down, then slowly pick off guys from the other team.
EDIT: And I hate hi caps.