Like most people who spend too much time on a keyboard, I have issues with repetitive stress, especially when mousing. To solve (well, postpone) this issue I have taken to using two mice. I switch frequently from right to left hand as pain and typing patterns dictate. On the right is my trusty MX Anywhere and on the left is the ROCCAT Lua Tri-Button Gaming Mouse. The latter is corded so it also gets more attention when the office is filled with robots and the wireless starts stuttering across the screen.
The Lua is lightweight and attractive with a standard 3 button setup. Left, middle, and right buttons work as expected and the scroll wheel is firm, but quite usable. There is a 4th button near the scroll wheel to adjust the DPI settings. You can switch from 250 to 2000 DPI with a few stops in between. This allows you to speed up or slow down the mouse on the fly. I found it a little difficult to hit quickly, but not impossible. Someone with smaller hands would have an easier time hitting the button on the fly for precision aiming in-game.
The mouse fits comfortably in my hand, and was comfortable on the pocket book as well. You can pick one up at Amazon or Newegg for about $30. You can read more about the Lua, or explore ROCCAT’s other models at ROCCAT.org