I am unsuccessful at finding the kids toy.  I owned one, maybe ten years ago.  Hand held, black plastic...<p>An artist named Paolo Salvagione made an arduino controlled &quot;string fountain&quot; a bit less than a year ago on this principle.  It would have to be dramatically up scaled to launch a paintball or similar.  His artistic interpretation was the vibration modes of the string look nice and artsy, whereas the engineering launch device I&#x27;m thinking of would be a perfectly non-vibrating circle.