my most annoying way to die is when you are up against 2 enemies, you get the double kill but you are damaged, oh look, 1 kill away from warthog, BAM, concussion or flash nade kills you because of damage you took from killing the 2 previous enemies
I hate joining a lobby with a game in progress, get owned by a player who is obviously very skilled, and then after the game hear the 12 year old kid who just destroyed me in the lobby. It's rare, but I'm man enough to admit, that kid has skill.
I hate dying after I apparently shoot someone point blank with a shotty, hear boom, see blood splatter, die half a second later, and on kill cam I apparently didn't shoot at all. It's happened to me a lot the last couple days while leveling my remmington up.