I use a Kensington Mouseworks which has a track ball (very good for fine adjustments during mixing and editing also means no wrist movement) It also has many programmable keys for shortcuts. I've set mine up like this. There are 4 buttons immediately around the ball I use the bottom left with my thumb as main left click the top left button with my index finger switches between edit and mix windows the top right button toggles my transport window and the bottom right button is normal right click. All without moving my hand. There is another row of buttons at the very top which I use for launching protools and my D drive which is where all my audio files are kept. I have buttons left which I havent programmed yet. This is where I bought it from.
http://au.kensington.com/
It also reduces RSI which I've seen engineers suffer from with normal mouses. It's also compatible with Mac and PC.