if you want cheap, I have a 2500dpi OCZ Equalizer laser mouse that I highly recommend, you can pay quite a bit of money for the better ones, the Equalizer is a really good price/performance ratio. For $19, it's a great mouse:
OCZ Technology | Products | OCZ Peripherals | OCZ Equalizer Laser Gaming Mouse
in terms of shape, it's a little more traditional, but sleeked just right I find, incredibly comfortable, it's got decent weight to it too, just the right weight to not be too heavy or too light
Depends on how you play, watch yourself when you game. Do you have your whole hand on the mouse when you are moving? Or just use your fingers? If you use your whole hand (like I do) then you want a Logitech mx518 or G5.. If you just use your fingers then you want something like the Razer's.