The brass coin squeeze ($(removed)) is a well-designed trick that I've been pestering my friends with lately. It consists of two brass tubes and a brass cylindrical block. The tubes snap together and the brass block fits between them. It looks like nothing can penetrate the tube, but you will show the spectator that you can melt coins right through the plug.
The trick comes with an excellent DVD that shows you how to perform a couple of basic sleight of hand moves (which are optional, but can be used to good effect when performing this trick).