You take a solid coin, bite it, and you show the coin to the spectator, the coin is now half because you took a bite of it, you spit out the other half of the coin that you have in your mouth back to the coin that you are holding in your hand. And the coin is now solid again, now the spectator is blown away! It would be a cool coin trick to do right? Now you can do that, you can even borrow a coin from the spectator and switch it and then perform the trick!
This bite out coin trick was first performed by the magician David Blaine. Since then it has been a really popular trick and many magicians started to do the bite out coins at parties and nightclubs, many guys do this to impress girls with their magic teeth!
Here is a short demonstration about the trick.