I just heard about and tried Prime Hack. It is pretty cool. It lets you play the prime games with keyboard and mouse, so it feels like a modern FPS.

I have only played with it for a few minutes as I am about to start work. But it seems really great so far. I need to look into the control scheme to learn some of the controls, but it was not difficult to figure out.

I think it also supports controllers as well, I will likely play it that way at some point.