I suggest:

-Serious sam 1, 2 and 3
- Duke nukem 3d
- Battlefield 2
- Orion dino beatdown
- Unreal tournament 2004 or 3

Daikatana .

Already did years ago.

Tyrian 2000.

I'm assuming you didn't read his preferences in regards to a story or graphics ;p

my suggestions if they haven't already been mentioned : Rise of the Triad reboot and Unreal Gold..also Hitman series if you are okay with some stealthy gameplay.

Already have your giveaway games but thanks anyway!

Shadow Warrior 2013 (playing it right now and it is better than original one)
Serious Sam series (any game but very light on story side)
Painkiller
Unreal if you don't mind something bit older.
I wouldn't be afraid to go with Crysis, North Korea x USA in there is not your standard military scenario at all. North Korea even isn't the only enemy there. ;-)
Also Dead Space 1 could be worth a shot?
F.E.A.R is good recommendation too.
Yeah and Black Mesa if you like Half-Life.

I wouldn't go with Spec Ops: The Line at all. It may have good story but gameplay wise it is very mediocre modern military shooter, which looks like something you don't want.

I am not in.

I'm in.

Rage.
Hard Reset.
Clive Barker's Jericho.
FEAR.
FEAR 2.

After reading req's for Shooter i know exactly which one you should not try - 3079 and 3089 - they both full of open world, inventory stuff and RPG elements. But they great anyway :)))

Is Jericho worth it? I am a HUGE Undying fan but I keep hearing that Jericho while not terrible does tend to fall flat.

Undying, Alien vs Predator 2000 and Alien vs Predator 2,Unreal Tournament.
I'm in.

F.E.A.R. gets my vote too, excellent fps/spookathon game.

Killing Floor, funky solo, brilliant manic fps action in co-op or online random groups, runs suuuuuuuper smooth!

Call of Pripyat ( http://www.gog.com/game/stalker_call_of_pripyat ) is open world, mostly, but not so much so that it isn`t a constant battle to survive. (or any of the other S.T.A.L.K.E.R. series)

Crysis games are good too, Newer the version, more strain to your system (I`ve a 6850 & they work well, although third I don`t run maxed)

Shadow Warrior 2013, Rise of the Triad 2013 or 2012 or wherever it got released, Serious Sam 3 - yeah, that should keep you entertained. Keep in mind that the new Shadow Warrior was just about the best shooter I have played lately.

Also, not in.

There are plenty of good old games around and both the Crysis 1 and Chronicles of Riddick are good games (played through both + the 2nd Riddick game). But id recommend you the new Shadow Warrior released last year. Good gun play, badass sword, some skills and spells + lots of tongue in cheek humour. There is plot, but its nothing that would tire you out.

Just keep in mind that the BFG Edition demands Steam.