I probably have more recent ones but I still think this is one of the most hilarious ones.
So I was playing Halo on the PC, I don't recall if it was my own server or not, but anyway I was driving the warthog with a passenger, and gunner, and we had the flag. I don't know if anyone remembers that map with a huge bridge in the middle, and there was also side bridges at the walls? Well we were on one of the side bridges heading to the portal to bring the flag. My A/V popped up minimizing the game, this held the gas and made the warthog go right over the bridge and into the pit of doom. When I scrambled to get back to the game, all I see is 3 master chiefs falling with a warthog, and the flag, and a bunch of "WTF NOOB" messages. I was killing myself laughing and everyone was mad and WTFing and explained what happened. They did not think it was that funny. I think we lost that game. Yeah, I said it. I just lost the game!