Chess games. It drives me nuts when anyone shows a chess match and a) none of the pieces' positions make sense, b) when they edit and the pieces are in suddenly different places where they could never get to, and c) when you actually see someone move a piece the way it can't be moved. I'm like WTF?

Incidentally, one of the reasons I love to watch the character of House play piano is because Hugh Laurie plays (really well, in fact) and it's always him they're showing.