Fun co-op/split-screen PC games?

Looking for some 2-controller-supported games I can play with my girlfriend on PC. Specifically FPS, RPG, side-scrollers, or something along those lines. Both of our favorite games are the Elder Scrolls series. Together, we've already played L4D, Borderlands, and Halo to death on our Xbox 360s so something besides those please! Neither of us have ever played Baldur's Gate, I was thinking of diving into that first...

Trine 1 and 2 are fun.

Sadly, there aren't a lot of options for that on PC.

really the only PC splitscreen game i know if is Portal 2

I believe most of the LEGO games have co-op/split screen on the same PC.

Magicka, Street Fighter IV- Street Fighter vs Tekken, Sonic and all stars racing transformed, Borderlands 2, Portal 2, Trine 1 and 2, Guacamelee... Those are the ones I've played. 

Btw -> http://www.co-optimus.com/system/4/pc.html 

Samurai Gunn! it's so much fun, pixelperfect murdering of each other..

I think Risk of rain has local coop play too... great, really hard rougelikelike. Both are on steam.

Check out these:

http://www.pcsplitscreen.co.uk/splitscreen.html

and these:

http://www.pcsplitscreen.co.uk/multiplayer.html

Oh, and check out Octodad: Dadliest Catch!

www.youtube.com/watch?v=321M7rURNIY

(Skip forward and watch him playing with his wife -- 2 players, only 1 character, each player controls a 1-3 limbs, which limbs you control changes randomly at certain intervals)

There are plenty of good games to play split-screen/co-op. Here's some of the ones I play with my brother:

- Megabyte Punch (a Smash Bros.-like brawler with highly customizable robot characters)

- PixelJunk Shooter (twin-stick shooter)

- Hammerwatch (a mini RPG with simple controls)

- Risk of Rain (rogue-lite shooter/fighter with some platforming)

- Beat Hazard (twin-stick shooter to your music)

- Guacamelee (Metroidvania-style platfomer fighter)

- Capsized (twin-stick shooter with some puzzles)

- Trine 1&2 (puzzle platformer with some combat)

- Monaco (stealth game)

- Towerfall (platformer fighter)

- Samurai Gunn (platformer fighter)

- Octodad: Dadliest Catch (I would put this in the next section but you use two controllers)

- Minecraft (you can use the joypad/splitscreen mod with Forge to use keyboard/mouse and joypads)

 

Some games that are good in turns or where you split the controls of a single keyboard/mouse:

- Goscurry (game where you control a vehicle on a changing path to the beat of some upbeat electronic music)

- Super Hexagon (difficult game where you move a triangle around a hexagon avoiding lines gravitating to the center of the screen to the beat of some more awesome electronic music)

- Rogue Legacy (a difficult rogue-lite platformer)

- Race the Sun (endless racer(?) where you fly a solar powered flyer on a map that changes daily. High score kind of game)

- Surgeon Simulator 2013 (name says it all)

Hammerwatch is a ton of fun

I liked Dead Space 3 coop. And Borderlands (2, didn't play the first one in coop).

Sadly there aren't many coop games in the genres I'd like :/ And when the game is story driven with a good campaign, a "coop" where you do some random missions not in the main game, that's not really coop to me :<

I think most of the Serious Sam games have split screen co-op, including 3.

Wow so many excellent recommendations thanks so much!

Yeah but dont you need to mod that to get the split screen to work?