I stopped using a regular computer mouse last year, replacing mine with trackball mice. Originally my motive was ergonomics: I work on the computer, and I relax on the computer–tendonitis is a very real concern .
I’ve realized in the last week that I fidget with the ball constantly. At home I use a Kensington, which has a poolball-sized ball that can be easily removed–which I do so I can roll it around in my fingers while I read. At work I have a logitech trackman marble, where I sometimes remove the ball but mostly just spin it back and forth.
I highly recommend trackballs to pretty much everyone, but especially to us pernicious fidgeters that can’t bloody sit still!