6 What's in the box?

1. A smaller box, which contains a still smaller box, which in turn has a smaller box. Make the player think this is a stupid joke but roll a d100. That is the final box, in which is the portal to a pocket dimension containing a dead sorcerers wealth. Any boxes past 20 or so will be extremely hard to open, requiring microscopes and special instruments and hired experts.
2. Your own severed head! Not really, it's just a wizard-joke. If you're unlucky you die of a heart attack. If you survive you find that the power source for the magic head illusion is a ruby the size of your nose. 
3. Skittles.
4. Wax. Inside the wax you can barely make out a dark patch of something. 50/50 chance it's nerve gas (lucky or lose one skill to permanent brain damage) or a magical bar of lead that when rubbed on food makes it taste delicious and nutritious. Turn anything masticable into a ration. The wax tastes like brown bread.
5. A tiny person has made it his tiny house. His will fire a tiny blunderbuss at the adventurers to warn them off while his tiny wife gathers up the valuables and runs out through the back door. 2d6 coins worth of tiny silverware.
6. Skittles, but just the yellow ones.