Right! I once did this in a game of Paranoia: put a bunch of red dice in the center of the table for everyone to use (this was a spontaneous session so people hadn't brought their own RPG gear), and one blue one. Of course, the blue die is above your security clearance. Any player that touches it has his character die for no reason. Meta!
I bought it at Das Spiel in Essen, if that helps.
(edit) search for "Smile dice" at Amazon.com and that's basically it.