Free MW4 http://mtxgear.mektek.net/MW4/download.html
Would actually be worth looking into if MTX wasn't currently such a piece of utter crap. Good luck getting it to connect to the master server, and if you get that far, good luck getting it to download anything properly via torrent.
The game was designed with the console in mind so I use a 360 controller. (I don't own an Xbox) Works great and its way better then any PC specific controller. I used the older wired controller since I don't really care to worry about batteries.
The X360 controller IS an excellent controller ... IF you have an X360. However, on PC, it's not so excellent and has quite a few issues. The drivers are basically worthless, for starters. You can't set deadzones, which is a MAJOR problem in every racing game on PC that doesn't support XInput (read: damn-near all of them.) You can't turn the triggers into 'buttons' which is a problem on most of the games you'll find. There are 3rd-party drivers (XBCD) that try to work around these limitations, but they don't support XInput (which is necessary for the controller to work with 'Games for Windows Live' games) and the drivers currently have a major bug where they don't report the stick inputs properly in most games you use it with, so you get really sporadic movements or none at all. It does work extremely well for emulators, though. Also, Xpadder is an absolute necessity if you have an X360 controller; you should check it out if you haven't already, Jeffy.
Using a wired controller is obviously the best choice for the PC player because it saves them an additional $50 that they would have to spend on the X360->PC wireless dongle. I mean, if I were gonna spend nearly $100 on a game controller for PC, I'd buy something pro-grade instead of the X360 controller. But at around $40 for the wired version, it's not bad at all.