I have a Tibetan ringing bowl beside this computer. I haven't figured out a performance use for it but I like to bong it every so often, it makes the same sort of long ringing tone leeneia described.

An even more private percussion instrument is the lid of a large wok. Balance it on your head and hit the rim. You get an amazing stereophonic gong sound.

Laurence Picken's book on Turkish folk instruments tries to apply the Sachs-Hornbostel classification to this sort of thing - most of the taxonomic space is taken up with children's toys. My favourite was popping a just-turned wet clay pot by smacking it flat with your hand.