Razer, the folks who gave us the BoomSlang unparalleled mechanical gaming mouse a few years back, had scoffed the optical mouse in its erratic infancy. They swore that they would not make an optical mouse unless they could make one that worked better than their mechanical mouse.
Well, time has passed and what was a new technology has become a commonplace technology, with great accuracy. True to their word, the folks at Razer have thus jumped into the optical mouse arena with their Viper optical mouse. (This leap was also pressured along by the fact that the high-quality mechanical mouse components use by Razer have become quite hard to acquire.) The Viper is smaller than its Boomslang predecessor, and has a higher arch to better fit the human hand. The Viper did, however, inherit the cool 'on-the-fly' sensitivity control feature, complete with on-screen sensitivity meter.
If you're not familiar with Razer's gaming mice, I've had my mechanical BoomSlang 1000 for something like five years. I just cleaned it for the first time right before E3 this year; It has a guard to keep dust and dirt out of the mechanicals that works pretty darn well. Also, the accuracy, consistency and range of sensitivity are amazing. Razer gaming mice are to be cherished. (Or envied and feared, depending on what you're gaming with...)