The Microsoft Wireless Natural Laser 6000 Ergonomic Mouse is a good choice. Sometimes people want a new mouse with their macs because the mouse that comes with them aren't designed for constant repetitive use. If that's the case, they might also want to consider a trackball, which will releive stress in the elbow and shoulder that comes from moving a mouse around. I use the Logitech Trackman Wheel.

I'm with Eric on the Logitech Trackman. It was recommended by my chiropractor and it has definitely reduced the pain in my shoulder that was coming from repetitive wrist motion.

Source: http://www.amazon.com/Logit...