You could always try digging up Halo 1 and 2, if you haven't played them a half dozen times already.
They're sort light on language (no F words, at the least), and I think you can mute the voices. Most of the language you'll hear in those games is from the marine squadmates you have.
Half Life, both of them, are good choices like Nate said.
I haven't played them, but I know the Battlefield series can be had on PC. I don't imagine the language is too bad in them (though I could be wrong. O_o).