I picked up an ION discover DJ the other day which I thought might be some kind of USB HID controller, but it's actually a MIDI controller, which is kind of cool.
It's got a whole bunch of knobs and buttons and sliders along with two spinning turntables.
There must be some way of using a MIDI device as a game controller. I'm still trying to wrap my head around how linux events work, it shouldn't be too hard to generate fake input events.
I'd love to use the turntables as a controller for tempest or something, or perhaps the dial for tron.
Just thinking out loud.