Gagein-it
Gagein-it happens when someone gets killed in a fight and another guy who was just watching decides to take out the winner because they're too busy gloating and too drained to notice.
I just got a kill and I was like, 'I'm the boss!' and then some guy I didn't even know shot me in the back.
He was high-fiving his friend and then a random dude snuck up and popped him.
I was winning and then some guy who was hiding in a corner shot me right in the face.