Rockstick 2 Vertical Mouse

The RockStick Mouse is an ambidextrous device that has been designed to use the entire hand to click, rather than just the fingers. This reduces the strain you place on your fingers, wrists and forearm when continually forcing your wrist into a downward and unnatural position with a standard computer mouse. 

Making small motions, you click from the hand and arm instead of with the fingers. This reduces muscle and/or strain issues. You place the mouse in your hand at a natural angle of 70 degrees.
The Rockstick 2 is suitable for left-handed as well as right-handed users. You can choose from a medium or large version, depending on your hand size.