Here is a nice close-up effect that every magician would like to carry in their pocket and perform whenever the opportunity arises.
You hand out a solid steel ball and a metal tube, to a spectator and then ask them to pass the ball through the tube. The spectator finds it impossible to do...
Now the magician takes the ball and the tube in his hand and make the ball shrink and slowly sink into the tube and rise up.

After the effect you can hand out the tube and ball for examination.