The Evoluent Vertical Mouse is by far the best and most popular ergonomic vertical mouse available. It has been a best-seller for many years and continues to dominate over competitors. This mouse employs a unique "handshake" grip that keeps your hand, wrist and forearm in a sideways position, which is more conducive to comfort.
The 3M Ergonomic Renaissance Mouse is the second best vertical mouse available featuring a very sturdy construction. Sometimes called the 3M Stick Mouse, this input device acts more like a joystick than its counterparts which some people find very easy to use. On the other hand some users report this mouse being harder to get used to than the Evoluent mouse.
Finally, the Zero Tension Mouse is also a popular ergonomic vertical mouse but its construction is not of very high quality. The defective rate of this mouse is relatively high compared to others, but it is a decent mouse. Users have reported increased comfort and decreased strain with this mouse, when it is not defective of course.