You need a lot of chessboards for this one, but on top of winning some money you will impress your pals.  Challenge a large even number of people to play chess simultaneously and blindfolded.  Ask for 2-1 odds against each opponent.  Play White against half and Black against the other half.  Even if your chess is crap, you are guaranteed to make money.

Here’s how.  You mentally associate each game you are playing White with a game in which you are playing Black.  You start with the opponents against whom you are playing Black and you remember their moves.  Then when you arrive at the associated board in which you are playing White, you just copy the move from the other board.  Wait for the response and then copy that move on the associated board in which you are playing Black.  Keep doing this.  You are effectively making each associated pair play each other.  You will average a draw on each pair and so with 2-1 odds you will make money.

All that is required from this is to be able to keep a few moves in your head.  If you can do that, you can do this blindfolded and really make an impression.  If your memory isn’t up to that, you can skip the blindfold and use the board positions as a mnemonic to help you remember.

Here is a video of this trick in action from Derren Brown.