A good one is when you've been jamming at someone and constantly stealing his blinds, and he bursts out, "keep on doing that you idiot, I'll get you eventually". Obviously, nine out of ten times they get frustrated and push with some sort of crap like top pair Tens, ace kicker. It's priceless.

Another one is when you raise some limpers with a hand like 67 and flop the straight, get all in vs. some sort of suited K with the flush obviously hitting on the river, and then have to hear the whole table going, "that's what you get for playing those crappy hands!"