I always liked the very electronic sound of dot-matrix printers with their stepper motors and solenoids.
G+: I always liked the very electronic sound of …
I don't even know how you would generate different tones with a printer.
Well, dot matrix printers where incredibly noisy when the were operating, mainly due to having a series of solenoids that physically smacked the paper through an ink ribbon. All you have to do is articulate the print-head at the right frequency and you get a tone. Since the print-head has usually 9 or 24 pins, you can use these for volume or polyphony.
The weirder ones are when people make hard-drive heads into speakers, such as in http://vimeo.com/1109226.