BFG Technologies' Sniper Boomslang 2100 on an Icemat Black.
The Boomslang 2100 is a ball mouse, but you wouldn't know it unless you turned it over (or used it on a slippery surface that won't grip the ball). My Logitech MX500 sits next to it on the Icemat, unused. None of the optical mice can compare to the 2100dpi resolution offered by the Boomslang, although the new Razer mouse comes close at 1600dpi.
2100dpi means I can move the cursor across my 1920x1200 screen with less than an inch of mouse movement and pixel-perfect accuracy. An 800dpi mouse requires 2.4 inches of movement to do the same thing.
The Icemat is made of glass with a slightly frosted surface to provide enough roughness to grip the mouse ball as well as provide a pattern for optical sensors to read. It comes with teflon tape for the mouse feet, so the movement is incredibly smooth (Teflon on glass, think about it...)
Nothing else compares, although Razer's new 1600dpi optical mouse is probably just right for most people. A lot of people struggle to use my computer when they first sit down at it due to the speed of the mouse, but I find the speed to be absolutely perfect for me.