After Dark for Real

You find a box in the attic.

This box contains a cube of glass.  All evidence indicates that the cube is solid.  Goldfish swim in the cube as though it were water.  The goldfish cannot be induced to leave the cube.

Weapon of Mass Fluffiness

You find a box in the attic.

This box contains a warhead.  Setting off this warhead will transform any battle within a mile of detonation into a pillow fight.

Laissez Faire

You find a box in the attic.

This box contains blank cards of the kind used for business cards.  If you use them to make business cards for your own business, they will be normal in every respect except they will form a contact poison absorbed through the skin, but only when touched by your business competitors.

Medicinal Trees

You find a box in the attic.

This box contains seeds of various kinds.  When planted and watered, they grow into trees.  Instead of nuts or seeds, these trees grow tablets of various medications: aspirin, antibiotics, codeine, and various narcotics are among them.