5. Feigning Death
This is admittedly a pretty bizarre function that appears only very rarely in video games, and even more rarely can it actually be employed in a game in a way that is useful. In the original Unreal Tournament and again in UT3, players were able to press F to assume the "feign death" stance, in which they resembled a corpse to any other player in the vicinity. It made for great fun when newer players who weren't yet used to the slight differences of the feign animation - compared to, you know, actually being dead - wandered aimlessly past, at which point you could leap up, murder them, and have a good 'ol laugh to yourself as they wondered, "What the Hell!?". Players quickly became savvy to it, though, particularly in the original UT; any dead bodies near a flag or a teleportation device would be shot for safety's sake, so you'd have to be pretty inventive about where you decided to "die".