I took the Sniper in Ragnarok, since no one else wanted it. Seriously, I didn't even rush that thing and it was the beginning of the game.
So I walk to the pelican side, thinking nothing, when suddenly a Mongo(ose) splatters me. Betrayal!
So, let me get that straight: I can't get shot by Friendly Fire, but splattering 'by accident' is alright. Because I took the sniper rifle some douche wanted. Alright.
I walked to that guy after I respawned and stood in front of him for two minutes, blocking his shots with my ass. Eventually, I couldn't be bothered and joined the fight (which we were already winning), to which he contributed shit, after all.
Or a game of Spartan Ops (Valhalla): This guy ran over me in his Ghost two times, so I mocked him and his Ghost with an EMP-blast and a few Plasmas, also destroyed his Mantis every time I had the chance. Not actively, but EMPing his Mantis while Banshees took shots at him. Great fun, indeed. I even had the highest score. What a joke.