*Good* Modern Single Player Shooters (PC Preferred).

[porous_shield]

Left 4 Dead 2 is a lot of fun but it only as a multiplayer co-op game since playing the game single player is insufferable with the Ai. I generally dislike multiplayer games and I ended up putting 200 hours into it.

It's quite cheap in the multiple holiday sales going on right now too, and for a side benefit, you can play Left 4 Dead 1 maps with Left 4 Dead 1 characters in Left 4 Dead 2.

 

[Denamic]

People have said it before, but Bulletstorm is really good. One of my favorite FPS games ever.

 

[Sandjube]

The new shadow warrior was pretty damn great, shooting and slashing your way through demons and shiz. Get that.

 

[Dandark]

I just got Bulletstorm in a Steam sale and have been really enjoying that so far. Maybe not a new game but it's still a lot of fun if you can get past the Gears of war style characters.

Although be warned that it has GFWL, it's still playable and I believe there is even a way to start it offline without GFWL if you really want to avoid it.