Those inquisative folks at Gamer's Block have word that it's possible to use the Sony PlayStation 3's Sixaxis controller for playing games on your Windows PC.  I have not tried this, nor do I know if it works as promised, but considering that I have linked a Nintendo Wii remote to a PC before, it certainly seems possible.  All you need is a special DLL file, an EXE file that acts as an installer (use at your own risk, of course), and a little spare time.

The PLAYSTATION®3 SIXAXIS controller can be used on a Windows-based PC (mainly on XP and Vista). You can play your PC games using the SIXAXIS controller as a PC game pad controller to optimize your gaming experience.

The Sixaxis controller is certainly light and comfortable to use, so I can see a definite advantage to using it for Windows gaming.  I have a Logitch Wingman for my PC gaming that, while it works, is also bulky, heavy, and over the years has developed calibration issues with the right control stick.  I'd just as rather use a Sixaxis on my PC than another weighty gamepad.  Besides, once Sony comes out with the rumored Sixaxis with rumble capability there will be a lot of used non-rumbling Sixaxis controllers sitting around.  Why not use 'em for PC gaming?