Fenixp: Right, DRM-free FPS games...
I will check, but I have heard that if you copy Half-Life 2 games out of the Steam directory, they will work as standalone copies. If you are interested, I will check for you by installing them on my computer and copying them over to another one, then I'll try to boot them up (it'll take me up to week with my current time constraints). If you're not interested in giving Valve money, I'll just carry on by saying:

Shadow Warrior. Yeah, the new one. I can safely say that it's one of the best first person shooters I have played in ages, it can be fully controlled via an xbox controller, and is a very skill-based game, so it also has a solid replay value.

The new Rise of the Triad. Personally I didn't like it all that much, but a lot of people seemed to, sooo... Yeah.

I'm not sure how far do you want do go in the old school department, but the original Doom 3 should be DRM-free too as far as I know (well, secured by a CD-key) - it might be worth checking on that one tho.

Other than that... Hm. It seems most of the good modern FPS games are Steamworks currently.

Elmofongo: Is Crysis 1 DRM free on Origin because everytime I install it a Shortcut of it always appears on the desktop so even when I am not logged into Origin I could still play it.