Okay, while you are trying to remember one to share, here's another one:

In your cellar there are three light switches in the OFF position. Each switch controls 1 of 3 light bulbs on floor above. You may move any of the switches but you may only go upstairs to inspect the bulbs one time. How can you determine the switch for each bulb with one inspection??

BTW, I am signing off for the night. My bet is that someone will figure out a good answer by the time the sun rises in West Virginia. Seeya then.