I use this:
http://www.pacificgeek.com/productimages/xl/W1668.jpg
I've used the exact same mouse for years and years and years. It's a ball-mouse with left click, right click, scroll wheel. I use it for gaming mainly due to the added friction (and therefore precision) from the ball that optical mice simply don't give me. I can't use the mice with buttons all over it either because I tend to hold my mouse REALLY hard during games for added precision and I always accidently click the 25 extra buttons.
The best part: these mice are typically $1.00 because no one uses them anymore.
If I'm not gaming at all, I can use an identical mouse with optical functionality. I cannot under ANY circumstances use wireless mice though...the lag (and it's there whether people notice it or not) in most wireless mice simply fuck me over in all games and even while using Windows. I haven't used a modern, expensive ($50-$100) wireless mouse so I don't know if the lag is fixed but the old school Microsoft mice that got so popular (that have even been mentioned in this thread) used to have a 5 millisecond or so lag that drove me insane.