This isnt exactly a commonly occuring glitch but it happened to me and its pretty funny so I thought I'd share.
I was driving out of Bohan on the East Borough Bridge and suddenly the guy infront of me slows as if he stopped accelerating, veers right and hits the partition. Keep in mind his car was in flames this whole time. He gets out and hes burning alive. I'm laughing my ass off and I would have gotten it on tape but it was on my Xbox version of the game.