A bad beat of a different kind
 

Signing up for a $22NLHE SnG, being amazed at some of the crazy play, enjoying watching them drop like flies, getting HU and being really impressed at your superior play (he was pretty weak), finally putting the nail in his coffin and seeing all the chips push your way, closing the table to view the lobby and...discovering you'd signed up for a $10 NLHE SnG. D'oh.

It still feels good to win but not when you realise you should have twice as much!