i found a great mental card effect in "Dear Mr. Fantasy" by john bannon that can be repeated over and over for the same people with no give away, and it is very direct. you do a spec peak, close the deck, pressure fan w/ the faces at the spectator, ask them to look at their card, and you can always tell what card they had. after a few rounds, john recommends saying "your not even looking at your card this time" and it just gets more impossible.