Logitech G500S, it replaced my Logitech G5 that I had for about 8 years before it finally broke down :P
Things are freaking solid.

Using Logitech G502

My other computer (which my wife has claimed) uses a Razer Abyssus

Zowie fk and can't see myself switching anytime soon. There is nothing to complain about, it gets the job done for any task. I like my mouse to be simple and the only other I've considered trying is the Logitech G100s which fits the bill for simplicity but I like have the side button for mumble =/

Teknet 2000dpi Wireless mouse.
It's okay, the abiliy to increase/decrease dpi in game is good when I'm too lazy to use the sensitivity slider
which is pretty damn lazy. Otherwise it's really a standard mouse just a bit bigger and more ergonomic.

Good for the price point.

Zalman M400 @ 800DPI

It's pretty good. Bought it because there is no mouse accel. Had it 4 years and going strong

deathadder since 5 years

I had a Deathadder, but it started dying a couple months ago. I picked up a Thermaltake Ventus for $20 on a Black Friday deal as a cheap replacement until after the holidays. I have to say, I'm pretty impressed with it. It isn't quite as comfortable as the Razers that I've had, but it tracks every bit as well, if not better. For 1/2 or 1/3 the price of a Razer I'm really happy with it. May I replace it down the line? Yup. But I'm in no hurry. Thought I was just getting it to use for a month or two, but now I could see me keeping it for a year or more if I keep having other stuff I need / want to buy.

Logitech G502: http://gaming.logitech.com/fi-fi/produc ... ming-mouse

Before that I had Steelseries Sensei. Both great mouses but after ~3-4 years of gaming with the Steelseries Sensei, the scrollwheel button broke, so I got Logitech G502.

It's hard to say which one is better, because I really like them both. I still use the Sensei with my other computer.
G502 feels a lot "snappier" though. Maybe a bit more accurate, even.

G502

(Military Green edition)

I love it to death. Would recommend.