Well if you're looking to play fps games with it, you'll want one that is wired, not wireless. I've heard good things about the Diamondback3G, and it has on-the-fly sensistivity which is once again great for shooters. I know many people have strong feelings about logitech but I have been using the G5 for a few months and it has been my favorite. To be honest, many people make a very big deal about the name on the package and not the quality of the product inside.
You can shove that OCZ Behemoth where the sun don't shine. I have one of those. It's hard to hang on to because of the slick finish for one. The finish makes it impossible to use skate board tape for traction because it won't stick right nor for too long. And I have a penny taped to the bottom rear because the thing likes to teeter front to back. JUNK !
I have used and owned several mice the past few years
Microsoft Sidewinder x8
Microsoft Sidewinder x5
And i have used random cheapo mice, such as the ocz equalizer etc.
I have finally found the perfect mice for me, the logitech G9x!, i set it up so its heavy at the mouse 1 button and lighter all around, so when i click my mouse stays still, and yet it still moves extremely fast. I play CSS Competitively and I have Since moved onto Tf2.
Another good mouse i would recommend that should be out soon, is the logitech G500, i believe its a remake of the Logitech G5 which was also a great mice i have used for a long time.