Shrinking Penny:

You are supplied with a shell penny, a very tiny penny, and a pen with a magnetic end.
Place the tiny penny on the underside of the shell penny. Pinch the tiny penny and the shell penny together with your thumb and index finger. Rotate your wrist so that the shell penny is facing up, and the tiny penny is hidden underneath. Place the pen in your pocket with the lid on the writing end of the pen.
Ask a spectator to hold out his or her hand, palm facing up. Place the shell penny and the tiny penny that you have pinched together in the spectator’s palm as one. Note: Be sure not to reveal the tiny penny when you place the pinched together  coins in the spectator’s palm.Tell the spectator that you will magically make the penny shrink right in front of their eyes.
Pull the pen out of your pocket. Tell the spectator to watch closely. Bring the end of the pen down towards the shell penny and then pull it away quickly. Count, “One.” Bring the end of the pen  down towards the shell penny again, allow the magnet to pick up the shell penny, and pull the pen away quickly. Count, “Two.”

When the pen is pulled away, use your pinky finger to pull the shell penny away from the magnetic end of the pen and hide it in your hand. Note: This move needs to be done quickly and in one smooth motion. When the  pen makes contact with the shell penny, say “Two”. This will help disguise the clicking sound the shell penny makes when it attaches to the pen. 

Bring the end of the pen down towards where the shell penny used to be and then quickly pull it away. Count, “Three.” The penny has magically shrunk! Put the pen in your pocket and ditch the shell penny as you do so.
Bonus Effect
As a bonus effect you can replace the tiny penny with a button, dime, or any other small object and make the penny transform into another object!

Learning Video: