A simple revelation you can do: get their card on top of the deck and give the it a few mixes. Show the top card, let's say it's a six, and ask whether or not they would be impressed if their card was six cards from the top.
Whatever they say flip over the card, take the top card counting 'one' before tapping it on the table and moving it to the left or right another five times as you count to six (in this example), as if you were counting out six cards. On the last number turn the card face-up to show that the top card has now changed into their selection!
All accomplished with a DL

.
Simple, but it really does work well.