One item that always scores a hit is the singing bowl. Children are fascinated and thrill-seeking (but usually clean living) Five Rhythms dancers can't get enough.
If, like me, you are fascinated by Tibetan singing bowls then this link to BBC News will interest you. It reports on research into the peculiar behaviour of water in the bowl when the instrument is sounded. If you have a singing bowl and have never tried this then give it a go.
The first bowl I acquired has a tiny hole in it so it is unsuited to this activity, at least indoors. Perhaps it would be prudent to hold your bowl over the sink for a moment while you check for leaks. Incidentally, my holed bowl is perfect and fully functioning in all other respects.
The BBC article touches on potential engineering applications when the physics of the bowls is understood. Perfume atomisers and fuel injectors are cited as early beneficiaries But so far, it seems, the Tibetan singing bowl has not given up its all its secrets.