Halo 3.
Me and a friend riding along on a mongoose in a team slayer match, and he has the rocket launcher. Good times ahead, right? Well, someone throws a grenade at us and it passes us by, then blows up, knocking us off balance. This was just as my friend shot the rocket, so it hit the ground right beneath us, we exploded, and the whole thing flew into a tree.
EDIT: I completely forgot about GTA 4. 2 here.
One, I was racing down a street on a motorcycle, chasing a limo I was supposed to kill. For fear of losing it, I looked behind me whenever it passed by and continued to shoot. Well, one time I hit a high curb. I was sent careening into a brick wall, fell a story, and survived. That is, until a car backed over me out of nowhere, going about 50 MPH. Backwards.
Second one is right after I get out of the hospital, I run across the street and get nudged by a car. I fall onto her hood, slide down a bit, and she proceeds to slowly drive forwards, and I slide under the car bit by bit. She ran me over at about 1 MPH. Slowest death ever.