Silverware (Stomp) Box
This one is made out of a thrift store silverware box. It measures about 15x11x3 inches and has 4 pickups spaced out inside the box, so you can tap different places on the box and get different sounds out of the amp. Uses a stand 1/4 inch jack so you can plug this right into your guitar amp, whip out your guitar/banjo/ukulele/mandolin/hurdy gurdy and add a beat to whatever music you're playing.
$35 + 10 shipping (in the U.S.)