WOBBLE STEEL GUITAR
This guitar-like instrument has a soundboard made of sheet metal. By a kind of body-shifting motion (admittedly a bit funny-looking) the player causes the soundboard to flex during playing. This causes resonance-shifts that color the tone in pretty ways as the notes sound. A couple of pickups – one magnetic and one piezo – are positioned to respond not directly to the strings, but to the vibrations in the metal soundboard.
You can just how funny-looking the body-shifitng motion is in a video demonstration appearing in this youtube playlist.