Want intuitive in an interface? Can't get much more intuitive than this: now-defunct interactive world-rhythm band D'CuCKOO (1986-1998, superceded by RhythMix) built the MIDIBALL:
a helium-filled balloon packed with wireless triggers so that the
audience could trigger sounds and images. D'CuCKOO also built bamboo
trigger sticks, marimbas and drums and even a giant interactive 3D puppet
that could animated with shows. One of the founding members even went
on to help create the incredible Mac visual synthesis software Studio Artist.
But you can't beat a balloon for simple interactivity.