Warning!!! you will look stupid if you do this. It's better to convince someone else to try it.

The Bet:
Stack three pony glasses on top of each other. The bottom one should have a shot in it. The top two should be empty. Challenge your sucker to lift the two top glasses and keep them suspended without the use of their hands (or anyone else's).

The Solution:
Light a match and let it burn a little then drop it into the first glass. Place your cheek over the top of it so that when the cigarette goes out it creates a vacuum. The glass will stick to your face. Repeat this with the next glass and your other cheek. Now all you have to do is pick up the bottom glass with your mouth and take the shot.