Co-op games for 2 players?

Oh wow, I didn't expect so many replies already. :o Thanks for suggestions everyone! :) I have narrowed the selection down to these:

ibb & obb
Orcs Must Die! 2
Magicka
Guacamelee! *
Dead Pixels
Gauntlet
Shank
Shank 2
Lara Croft And The Guardian Of Light

I already have games marked with * and games marked with ** are on my wishlist.

If you have any other suggestions, feel free to post them.

A little note on other common suggestions - we're not into racing games, Saints Row and Lego games.

The original Trine now has co-op.
Capsized's controls take a couple mins to get a handle on but isn't too tough.
Monaco can get manic and chaotic but definitely doesn't require precision.
The Sanctum games are very straight forward in the shooting department so the tower defense aspect may be enough to hold her interest.
Playing with someone experiencing Minecraft for the first time can be refreshing.
On a similar vein Terraria lets you have most of Minecrafts creativity with a clearer progression and endgame.

Brothers - A Tale of Two Sons

I haven't played, but it's got excellent reviews.

Brothers: A Tale of Two Sons, Battleblock, Monaco, Spelunky,Orcs Must Die 2, Lara Croft, Full Mojo Rampage, PID, Guacamelee

RunersRouge-lite, but if you're playing Hammerwatch, you should try this too.
Cook Serve DeliciousOne play as cooker and other as expedites orders, can swap anytime.
Defense Grid 2A Tower defense.
Van Helsing 1,2As you already like Torchlight.
Sonic & All Stars Racing Transformed A Mario-Kart, you can play local-co op in campaign. You didn't like racing though.
JujuNewly released, It's look like Trine, I think?
Dynasty Warrior 8 Pure hack & slash.

Magicka has a lot of fun even for 4 players. My number one recommendation.
Fear 3 you can do the campaign coop.
Broforce is hilarious.
Risk of Rain is HARD! But nice to play, specially with a friend.
Borderlands (all of them).