I saw 2 horrible beats this weekend in a 2-5nl game in a casino:
#1: A girl hits a set of nines on a board of K9x. She bets and gets raised. She reraises and the other guy insta pushes all in. Obviously, she calls and shows her set. He shows AK. Turn=A, River=K.
Then, about an hour later:
#2: I can't remember the betting, but a guy with QQ hits a set on the flop after calling a raise. He traps the initial raiser, who moves all in on the turn when a jack hits. Neither shows until after the river, which is another jack. The victim proudly says, "queens full", to which the other guy says, "quad jacks". I don't think I've ever seen such a disgusted look on anyone's face at a poker table.