One of my least favourites is the one where we see a head-shot of one character in a conversation and it goes on for a few seconds too long, which automatically tells you that the other person isn't in the room and the character is practising his lines in the mirror.
There's a related shot where we see both characters only from the neck up for a couple of moments, heralding a "surprise" reveal that they're naked, or wearing strange costumes, etc.