There are plenty of cool Stirling engines you can buy for experiments or teaching science. This Stirling Engine Marble Tower is pretty special though. It uses a Stirling engine to power a marble machine. An alcohol burner is used to heat a cylinder. Once the engine and its pistons are set in motion, the marbles are raised to the top and come down until they are picked up again.
This machine has a footprint of 13″ H x 9 1/2″ W x 8 1/4″ D. Not cheap though.