I'm running a Rise of the Runelords campaign here on the boards and had an idea that was too good to not use. We just made it the end of the first set of encounters, one of which involved a goblin stripper/dancer/singer/barbarian named Krosk. His first action on the field of battle was to rip off his pants and begin pelvic thrusting in a black thong.
Needless to say I am racking my brain to try and top myself.
(For the curious, here's the post where he enters.)
So, what kinds of shenanigans have you pulled that have scarred the other players and/or the GM? I'll be taking notes. :D