Jean Shepherd (of Christmas Story fame) told a story on his old radio show about finding an "electric therapy machine" in an old trunk in an attic. The kids had a grand old time shocking the bejesus out each other.

I've seen several of these "therapy machines" since. They were variations on a simple dyanamo/magneto and they hurt! They were in lovely wooden boxes with beautiful illustrations of the machine being used to cure the ailments of "The Crowned Heads of Europe" or some such thing. Think crank-telephone kind of shock. Nasty.