This one was a glitch, but I damn near pissed myself. Waaay back on the GameCube, I was playing Medal of Honor: Rising Sun. It was a conflict my grandfather was a part of, so I wanted to play it. There was one point, I think it may have even been multiplayer. In the baseball field, where the announcer usually would be, was a machine gun nest. You could get up there and cause some trouble for the folks down below. Anyway, as I was using it, I must have pointed it at some weird angle, because suddenly there were floating eyes and teeth in front of me. I nearly threw my controller. Apparently, I was seeing the inside of my or an ally's head, but was clipping through, so only the eyeballs (facing me for some reason) and the teeth were showing. Holy... crap.
I'm sure if I went through the thread I could find plenty more, but that one is the first to come to mind, and WAY off in terms of being a scary game. As for actual game events, I'd have to think before posting again.