tell em, "if you dont pick a card, I'll have to cut you up with an old dull axe that I keep in my woodshed, oh and if you dont pick the right card, lets just say a gun will be part of my act."
you took my line!!!!!!!!!!!!!!!
what you do is, do the riffle shuffle really fast, telling them to tell you when to stop. you come to the end of the pack and they havent told you to stop, say "lets be a little faster next time." then do it again, same speed(really fast) so that he doesnt have time to say stop, then say, "we a little slow today?". then do it fast again, and this time say "ok can i get someone up here who doesnt have down syndrome". ok leave that part out, but you get the idea, just have some fun with them, but dont make fun of them like with the down syndrome, that was a joke.