The magician borrows a banknote from a spectator and asks them to sign it with a regular ball point pen. The magician then takes the pen and plainly stabs it through the banknote, the penetration looks extremely fair and can be viewed from both sides of the note. The magician then pulls the pen out and hands the banknote back for examination, there are no holes in it anywhere. The pen can also be handed out for examination with nothing to be found.
This is a really nice stand alone effect or a great introduction to a banknote routine.