I like the standard 2 button+scroll wheel mouse, preferably optical. Make and model doesnt matter to me.
Only other style mouse I've considered has the ball on top, with the buttons being clicked by your thumb and pinky. You use your other fingers to roll the ball around, and the mouse itself stays fairly stationary.
On the subject of mouse balls:
Note: This was an actual memo
Date Created: 08/16/89 01:19pm
Author: Richard Landiner
Title: MOUSE BALLS NOW AVAILABLE AS REPLACEMENTS
If a mouse fails to operate, or should perform erratically, it may be in need of ball replacement. Because of the delicate nature of this procedure, replacement of mouse balls should be attempted by trained personnel only.
Before ordering, determine the type of mouse balls required by examining the underside of each mouse. Domestic balls will be larger and harder than foreign balls. Ball removal procedures differ, depending upon the manufacturer of the mouse. Foreign balls can be replaced using the pop-off method, and domestic balls by the twist-off method. Mouse balls are not usually static sensitive, however, excessive handling can result in sudden discharge.
Upon completion of ball replacement, the mouse may be used immediately.
It is recommended that each service technician has a pair of balls for maintaining optimum customer satisfaction, and that any customer missing his balls should suspect local personnel of removing these necessary functional items.
Please keep in mind that a customer without properly working balls is an unhappy customer.
Learn something about everything, and everything about something.