I used to use a Razer Diamondback Plasma mouse, which was a good size, very lightweight and really responsive.

I used a friend's Logitech MX Revolution and after getting used to the added weight of the battery, I liked it enough to buy one and it's the one I use regularly now. Besides reducing the amount of cables trailing around your PC being a wireless mouse really isn't much of a selling point, but it's a quality mouse with good battery life and charges quickly.

Of the two I feel the Razer probably makes the better mouse for poker, but you couldn't go wrong with either.