This effect has become a very popular one with magicians ever since David Copperfield presented it on one of his TV spectaculars. It is the visual and incredible penetration of a borrowed note or bill by an ordinary pencil with everything performed in front of the spectator's eyes.
In effect, the performer borrows a note. This is placed over a piece of paper of the same size and creased in half. A pencil is pushed through the note and the paper. The crease is opened out, and the audience can see the pencil going right through the borrowed note and the paper from both sides. The pencil can now be pulled away, ripping through the note and paper at the crease.
Yet when they are opened out again, the ordinary paper is found to be ripped as one would expect, but the note is in tact and totally unharmed. The entire effect is so clean and convincing that the audience can't believe their eyes. Yet it is quite easy to perform, requiring only a few handling trials on your part.