In keeping with Kent's theme of intelligence, I found a great video podcast a while back about a street magician whose primary focus is critical thinking and skepticism. Brian Brushwood's podcast is called, Scam School and is part of Revision 3's hosting services.
The episode entitled, House of Nails, is about being able to balance about 10 nails on top of one vertically mounted nail of the same type. I've been aware of this "trick" for almost 15 years thanks to Charlie Blair-Broeker back at an institute at Nebraska Wesleyan.
You can show the videos in class or learn them yourself (he shows the viewer how every trick is done) and amaze and astound your students. Because he does his work on the street or in a bar, you may want to learn the tricks yourself depending upon your district and judgment. Do at least check them out and enjoy trying to figure out--they are great puzzlers for those of us who need to do brain exercises. :-)