About two years ago, a guy posted a how-to for turning old NES cartridges into a harmonica. If you lack the tools, know-how or NES carts to make one yourself, someone's now selling them, for $US24.99.
I don't know if the seller is the same guy, and I'm not saying someone took another's idea. All I am saying is, two years later and fully in the throes of the global recession, harmonicas are definitely a top-trending musical instrument. And everyone who wants to can hum a few bars of of the Top Gun anthem or the Super Mario Bros theme - using those games. And that's awesome.
NES Harmonica [Makers Market, thanks Ryan]