Show two small, identical sets of five ESP symbols to the audience and hand one set to a volunteer. Claim that you'll be able to read his mind and influence him in his subconscious when he makes his choice.

Then mount your own five ESP cards in a well-defined order in a holder. Your audience can only see the backs of the cards and, as a result, don't know the sequence. Ask the spectator to tell you in what order he wants his cards placed in the holder. It is his choice entirely and he can chop and change as much as he likes.

When his cards are in place and the holder is turned round, your sequence, for all that, is found to tally perfectly with his.

An incredibly good trick which, nonetheless, is dead easy to perform.