I use a Logitech Cordless Optical trackman, got buttons up the ass, you use your two middle fingers and not your thumb, stay away from that kind, pain in the ass with games. The one with the ball in the middle is the ONLY one I will ever use. It makes games easier for me, especially some of my bowling games, or shooting games. You dont have to keep picking up the mouse and re-setting it like you would with the "normal" kind, and with mine you can assign the buttons which there is about 8 of them. Battery lastes many months and I use it 12-14 hours a day, everyday.
I also have the marble mouse, it was my first Logitech one, its good two, again uses the two middle finger, or one

, and works well for games too, just less buttons and its a usb so no wireless, but at $20~ vs $60 it would be a good one to test the waters with. Can be found at justdeals.com or ebay for a good price. Also if your a gamer of the 90's you will come to love the trackball over any other kind no matter what once you start using it, and adjust it to your liking. I havent used a regular typer mouse as my main in over 8 years after I got my first one from Compusa, a 4 button clear one that lit up. for $20, after that day, I was hooked and no going back, made anything you did on the computer sooooo much easier, and more precise control, at least for me.