Now here's a toy I really want: a levitating train. Just take a superconductor, add liquid nitrogen, and you've got a floating train! This video is in Japanese, but you don't need to speak the language to enjoy the effect. (The train starts moving just after the 1-minute mark, after ladles of liquid nitrogen have been dumped on it.)
Note: Do not try this at home...or at least put some gloves on when handling liquid nitrogen!
For more on this effect (including equally impressive videos), check out Quantum-Locked Superconducting Floating Discs Will Freak You Out.
(Via Laughing Squid.)