Brian Wilson of the Beach Boys used the theremin to great effect in the song Good Vibrations. Other bands to use the theremin include Portishead, The Polyphonic Spree, and Nine Inch Nails. Robert Moog has said that the theremin was what got him into the Synthesizer business. There There is still an extensive theremin community. Some audio samples can be heard here and here. Thanks to goofyfoot, Wolof, and SideDish for the inspiration.
The Theremin was invented by Lev Sergeivitch Termen (anglacized to Leon Theremin) in 1919. It uses Electromagnectic Induction to control pitch and volume. It produces an eerie, whistling sound associated by many with early horror films.