I was playing Oblivion on a friend's PC for a bit. After getting bored of swimming, I got out on land, and started running. For some reason, the breath bar kept draining. I was out on flat ground, could swing my weapons, etc, but he wouldn't FUCKING BREATHE! The result was seeing his final choked gasps as he fell dead on the ground from dogged determination to hold his breath.
Runner up goes to San Andreas, when I was in Grove Street, gathering homies for a particularily brutal assault on enemy territory. After collecting my posse, I began running toward the car which spawns in front of CJ's house, ignoring the sirens behind me. Lo and behold, an ambulance came out of nowhere, splattered all my gang members, and me, then drove out on the same fucking road in on which it drove! It came all the way over to Grove Street and did a U turn just to make my life difficult. I did survive, but I still feel it's worth noting, as none of my gang did.