Aquasonic waterphone. I recognized one of the sounds it made as being the brontosaurs from Jurassic Park! Also, I think this is so awesome because I like to put water in frying pans, hit them with silverware, and swirl the water around to vary the pitch. Enjoy:
You gotta wait through some product crap at the beginning of this one, but it's well worth it for the mini-concert! The theremin can be really creepy sometimes, but in this one it sounds like an opera singer:
People used to think the glass armonica's sound would drive you insane because of the wacky things it does to human hearing (the range of frequencies it plays at are such that the human brain cannot tell where the sound is coming from), but it was only ever the players in danger of insanity (they used to use lead glass). Sounds awesome, though:
EDIT: Speaking of unusual instruments, how about learning how to play a building?