A bit weird, but a RollerMouse Pro (http://www.rollermousepro.com/ http://www.rollermousepro.com/). I got it once while fighting a bout of RSI and it's a bit w

A bit weird, but a RollerMouse Pro (http://www.rollermousepro.com/ http://www.rollermousepro.com/). I got it once while fighting a bout of RSI and it's a bit weird but I really like it. I had a mouse next to it for quite a while but after not touching it for a year I'm now all in.