Leechin' to show the Logitech MX518, the best mouse ever created.
This really is a great mouse. Unfortunately, years of using a
logitech trackball have just about ruined my ability to play games with a regular mouse. With the trackball, your distance aiming will suffer, but your dretch wallwalking ability will go off the charts

since the thumb is more agile than the wrist. Plus, no more moving the mouse to reposition. Of course, my aim has always sucked, so maybe its not the trackball that causes that.

I use it because with my job I use a mouse all day long, and my wrist was starting to hurt constantly. That pain went away the day I bought a trackball.
If you are on a computer all day long, I'd recommend it. If you mostly just game, I'd definitely take lava's suggestion.