One of most amazing things I every saw done watching Mr. Wizard was when he cut a hole in a piece of 8 1/2 X 11 inch paper that you can actually walk through with the paper still being in tack. Every time I show a child it simply makes them think they have seen the impossible. You can see it done in the following link to a youtube video. Try it yourself. It's really easy.
http://www.youtube.com/watch?v=BQEz9Lpugsk Have fun.