Let's see, there are several times where I've gotten pissed off cause of a game, but none that I can remember off the top of my head.
I gotta say that sometimes playing online pisses me off, depending on the people you meet.
Me and a friend of mine were playing Halo 3 Team Slayer with these two other guys, and we're all doing alright, when these losers ON OUR TEAM start calling my buddy a pussy for using the sniper rifle, telling him to get out there and charge cause he's not getting enough kills.
At this point they don't have any more than we do, so we ignore them. Eventually, one of them is at the top of our team's kills, the other is on the bottom, and we're in the middle. They're all charging in, and I'm covering them with sniper fire. It's not going all that great, but they're bitching at me to charge in with them cause I'm not racking up enough kills, even though I've just saved their asses 3 times with the cover I'm providing.
I get fed up and tell them "I'm not racking up huge kills, but I'm not dying nearly as much as you are." The top guy's response is "Who gives a shit, kills are all that matter!" I tell him "Not in a team game, not if they're killing us faster than we're killing them. Staying alive is just as important." His little friend who's doing worse than anyone on our team chimes in calling me and my buddy (who was actually working with them) all sorts of shit, just yelling so nobody can talk. I can barely tell him to "shut up and pay attention to the score" cause he's screaming so much.
The match ends, we lost, they yell at us like we just gave Al Queida the fucking bomb, and I make them avoided players. I know this is nothing new to Halo, or Live, but GOD, I really can't stand people who start acting like fanatics over a game and turn everything into a yelling match where their ammo is mainly "Shut up fag" and "You suck, pussy", believing that because they're louder, they're right.
So that was something that angered me beyond reason. Literally beyond reason, because it's really not in my nature to waste my breath on morons like that.