I'm perfectly happy with this little guy from Logitech...
I got him from BestBuy for $9.98 because his previous owner returned him for some unknown reason, and neglected to return the drivers CD, and also stole the AA battery that made a LED go blinky blink in the box for display. I just downloaded the drivers free from logitech and saved $20 (retailed for $30 at the time).
I personally hate large miceses that you have to rest your wrist on, which forces you to move your entire arm forward/back which requires too much effort. Maybe I just have a small hand or something, but this mouse is perfect.
You also can't go wrong with a Logitech First Mouse if you want one with balls.