i use the intellimouse explorer, the original grey one with 2 thumb buttons, a scroll wheel and its optical of course...you know what im talking about.

its lasted me since i first bought it 3 years ago. the usb cable went bad, so i switched out the cable with a microsoft usb ball mouse that i had laying around, and it works great still today. but im thinking about going the next explorer version, the wireless one thats a bit more sleek and has another thumb button....