If you take your Unreal Tournament and Quake III deathmatches as seriously as you should, then you'll definitely want to check out the Razer Boomslang high performance gaming mouse. Available in 1000dpi and 2000dpi (!) versions, the USB Boomslang sports 5 buttons, a scrollwheel, and a superior low-wide, contoured shape that fits the hand perfectly...just as a semitranslucent device of wicked annihilation should...Included in the unique, round, foam-lined "tin" that it ships in are a driver CD for PC, a USB->PS/2 mouse port converter (also for PC), and the docs. Mac drivers are in the works and should be available on Razer's site any time now, but until then you'll be satisfied plugging it right into your USB port and going ahead (basic functionality is there right off) or better yet by getting a copy of Alessandro Levi Montalcini's excellent control panel, USB Overdrive, which lets you configure all aspects of the mouse, or any USB pointing device.
I ordered a Boomslang 2000 as soon as I heard of it, and I must say, it is indeed the finest mouse I have ever used, and I've used a few... A worthy addition to any serious gamer's arsenal, to be sure.