If you want to make a fun game to stump and annoy your friends, make a box with a simple target on it, say one foot square. Hidden in the box, mount a strong neodymium magnet, 2 or 3 inches in diameter, 1 inch thick or so directly under the center. Put the box on the floor and let them pitch coins on it, trying to hit the bull’s eye.
It’s not impossible, but the dynamics will be all messed up.
(Coins with iron will give away the trick.)
Edit to add: CAUTION! Magnets of this size can be very dangerous to handle. Use caution!
