I was playing socom, my third match ever. I had been playing with a friend in some small user created matches. He decided I was good enough to fight on my own, so he spectated a game with me and this other guy versus a clan of four. I told the other guy about my newness, and he said "that's okay, I'm here to teamkill you" When the match starts, I, with the three factors of that threat, the fact that I was new to the game, and he was wearing some weird ass camo, shot him right in the head.
I apologised, not knowing if he could hear me from beyond the grave. (it was a no respawn room) I ambushed and killed one of the other clan, than ran to a little defendable corner when the other three chased me. I killed two, then tried to blow the other one up with a nade but instead killed myself. My teammate later congratulated me on headshotting him within a second of the game starting, so this doesn't really count.