Hi hbm and a very warm welcome to sevenforums
See my post, number 9 on this thread. It's not a mouse with a ball on the bottom but a ball on the top.
I'm using one right now and it's great, fast and precise. As the body of the mouse doesn't need to move at all (although it does move quite easily on a smooth surface) you don't have to worry about mouse mats or the surface underneath at all. The ball is easy to remove for cleaning.
I've tried a couple of expensive gaming mice and I perform better in games with this so I always return to it.
They also make a wired version, which is what I use.