Bowling Ball from Briefcase Trick by Timco Magic (watch video).
The magician walks onstage carrying an ordinary briefcase that he puts down on the table. When he opens it up he removes a full size Bowling Ball, Basketball or Pumpkin. You can also make a different large item that cannot possibly fit in the briefcase appear. After the production the case can be shown all around.
This is one of the funniest props for the comedy magician. Can also successfully be used by a clown or M.C. This is an improved version of the effect where you can show both the inside and outside of the briefcase at the end of the effect.
Bowling Ball from Briefcase Trick by Timco Magic (watch video)