COD:BLOPS earlier today, on Nuketown CTF. Spawn upstairs, decide to dive headfirst out the window. I land perfectly on my belly, not two feet from an enemy who was running that direction. I let loose a burst from my rifle, but he'd seen me and had been tracking me all the way down.
In all actuality though, the funniest deaths I've ever had were in GTA4 after I beat it and started using cheats. Nothing quite like getting into a firefight on Liberty Island- no infantry ever spawns, and the boats are too far to do anything. The only danger is helicopters- and with the weapons cheat it was open season. I was just about to spawn my own and leave, so I fired off a last shot at an enemy chopper. Beautiful hit- caught it right in the tail. This pilot, though, was smarter. The chopper spun towards me and started flying forwards. The chopper was going to hit beside me, though, so I wasn't worried about it. It wasn't until a moment before impact that I noticed the problem- the main rotor was still spinning. I died from a rotor to the head moments before the chopper slammed to the deck and exploded. I actually managed to get video of it, and if you guys are interested I could get it out.
EDIT: WAIT HOLD UP forgot a good one. (I'll try to keep it short)
Bad Company 2, Valapariso map, last point, attacking. Blackhawk spawns, and I'm an alright pilot, so I grab it and start into the enemy base. They've got a guy on the MG and I take some pretty serious flak before I get close, and I can't get away now. My only chance to salvage this is to ditch the aircraft on somebody. The busy middle section is my target. I cut the throttle and swoop in, jumping out just too late. I die from fall injuries. However, the chopper collides with someone and kills them. The best part of all this was how the game recorded the death. Not death by physics, not roadkill but Death. The game had no damn clue what I had just done. I assume dropping helicopters on people wasn't part of testing.