I prefer flanging, myself

Oddee has 10 Most Bizarre Musical Instruments:

The frequency and combinations at which a participant interacts with her sensors can not only escalate her moans to a full scream but also apply additional audio effects such as delays, slicers and reverbs. These sensors are then fed into a i/o controller board that communicates with custom software written in Max/Msp. All software processing is done inside a mac-mini hidden in a small box near her feet. This box also houses her speakers.

I only quoted that part to make you click the link. The other instruments are less titillating but no less (perhaps more) fascinating.

Due to the photo (and the video too, I suppose) of the first, er..."instrument," this post is NSFW.