I just picked this little thingy up the other day:
It’s a NuLOOQ from Logitech. It a weighted dial with some buttons and a scroll wheel on top. Used with Photoshop it lets you zoom in and out with a twist, increase/decrease your brush/eraser diameter with the spin of the finger, move around your art with a nudge, and some other stuff I have yet to figure out that look like a lot of fun.
I colored two cartoons this morning in record time my first time out. I wish it were just a smidge heavier, but the glowing blue lights make up for it.
Seriously, this thing is great so far. Used in conjunction with my graphics tablet I save a lot of keyboard shortcutting and toolbar tinkering. Plus I look all space-agey when I use it!