Fellow claw-gripper here.
HUGE advocate of the CM Storm Spawn. This mouse was built for claw-grippers such as ourselves. The ring finger rest is quite nice once you adjust to it. Makes using other "standard" mice feel weird now. It's a fairly light mouse (approximately 86g not including the cable, IIRC) with a very nice rubberized side for some added grip. The optical sensor is great; using FW32, my lift-off distance is less than 1CD on an Artisan Hien mousepad. Pretty good stuff!
Drivers let you modify the side and top buttons to whatever you want, which allows for some great customization. In StarCraft II, I've mapped the default DPI buttons to hotkeys 7 and 8 and the side buttons to 9 and 0. Makes it a lot easier to access those hard-to-reach control groups. You can also choose from three firmware versions to best suit your gaming surface. As mentioned before, FW32 seems to have the best results for me. YMMV.
The "Great Deals" subforum had it priced at $30 with a $10 rebate if you ordered from Newegg. Not sure if it's still valid, but you can check it out for yourself. http://geekhack.org/showthread.php?27501-CM-Storm-Spawn-20-after-Rebate-OR-Xornet-17-after-Rebate
Alternatively, you can go with the Logitech G9x, naked (no weights or shells, just the bare mouse). Laser mouse with built-in hardware acceleration. You either hate it, get used to it, or not notice it at all. I don't have any experience with this mouse as I was hesitant about shelling out double the price of the Spawn for something I wasn't sure I would like. That being said, a lot of people here love the G9x and it's become one of the forums' favorite laser mice for RTS games.
There are a lot of other mice out there, such as the Razer Abyssus, Zowie Mico, and others that people love to recommend for claw-grippers. Here's a couple threads to help you decide:http://geekhack.org/showthread.php?21969-What-your-fav-mousehttp://geekhack.org/showthread.php?26764-Best-RTS-Mouse-With-No-Acceleration