I have a funny/really weird moment from Halo 2:
I was playing co-op with one of my friends, and we saw one of the marines kill another one, which rarely ever happens. So I said, "Did you just see that marine kill that other one?". Then the marine that killed the other actually said, "It was him, not me!", and it pointed in the direction of the screen, so it looked like he was pointing to us. It was strange...