Logitech MX Revolution.
Got it for X-mas after wanting it for over a year. Yeah baby!
I love thing thing for so many reasons.
First, it's the most comfortable mouse I have ever used or held. It's ergonomics are superb and the build quality and materials used are very nice. It has rubber inserts for your thumb to rest, the primary buttons are a one piece design, and the other buttons are nicely finished.
Then there's the scroller, which is quite amazing. It's made out of alloy and not plastic with rubber grip in the center. It features what Logitech calls SmartShift technology, where the mouse can switch between from normal scrolling to nearly frictionless scrolling, that is the wheel can spin freely. It makes scrolling through documents a breeze. In addition, it can be tilted left and right to scroll horizontally. It also has back and forward buttons as well as a search button.
The wheel on the side isn't a fully rotating wheel but rather you can push it for and aft to flip through documents. Sounds kinda gimmicky but it really is far quicker than selecting the document from the taskbar, especially when you have a lot open.
It's also remarkably precise, looks awesome (as I said before) and has a rechargeable battery that has an impressive life cycle (I have yet to drain it more than half). It also connects to the computer faster than most wireless mice
One of the coolest features in in the software that comes with it. SetPoint lets you set the functions of each button. By default these settings remain the same for every program, but you can customize the button functions for each and every program. So, for example, back and forward on Firefox can be Cut and Paste in PhotoShop. It can also hold profiles for other types of mice, like say a dedicated gaming mice (although this works fine for gaming), You can also customize all of the speed sensors of the cursor and when if at all, to engage SmartShift. You can even have dedicated game profiles for the mouse.
Oh and I finally have a mouse to match the rest of the color scheme of my desktop
There's only one flaw I've noticed. Because you press the wheel down to switch between stepped and frictionless scrolling, there is no middle mouse button. Normally this isn't a problem, but some games like The Sims 2 don't let you change the controls and the middle mouse button is an important camera controller. But with some ingenuity it can be worked out. Most games it's not a problem though.
Finally, it's a Logitech. My experiences with their products have been excellent. They are durable, well built, good looking, and far more substantial and overall superior to the Microsoft mice.
Sorry to sound like an infomercial, I just love thing thing!