Dust: An Elysian Tail - A enjoyable 'metroidvania' platformer with fast combat, upgrades for your character and a cute catlike bat thing that follows you around.
Hotline Miami - Topdown shooter with a great 80s soundtrack, intense unforgiving combat that gives you a challenge.
Mount & Blade: Warband - Start from peasant and climb your way to king/queen, gather a band of jolly screaming nord huscarls and watch the axes fly...
The Chronicle Of Riddick: Escape From Butcher Bay/Assult on Dark Athena - Escape from butcher bay was a lot better than Dark Athena, but for first person stealth and melee there are really no better games for this. I honestly wish more games where made like Escape from butcher bay.
I agree with these
He who stumbles around in darkness with a stick is blind. But he who... sticks out in darkness... is... fluorescent! - Brother Silence
If you ever want to co-op on SRIV or Sniper Elite, let me know. http://steamcommunity.com/id/InfantSandwich/
As far as recommendations go: Total War: Shogun 2 Terraria WB Humble Bundle Sniper Elite: Nazi Zombie Army is good for co-op if you can get it cheap Skyrim (with mods I'm using 2.5 GB of my VRAM, and it is delightful) The Binding Of Isaac Left 4 Dead 2 (Grab it during a Steam Sale) Far Cry 3
Ys: The Oath in Felghana - An excellent Action RPG with some really intense boss fights and superb music. Music example: http://www.youtube.com/watch?v=TXHtkHlLcxQ
Ys: Origin - See above, only there are three story modes each one giving control of a different character, which play very differently from each other.
Ys: 1&2 Chronicles + - A remake of the first two games in the series. The combat is pretty dated, but can still be a lot of fun.
Half Minute Hero - The main mode crams every RPG convention from talking to NPCs in town to battling bosses into 30 second segments of frantic game play, which requires good planning to complete.(the timer can be reset if certain conditions are met and is frozen in town) A very unique game, which also has great music.
Mark of the Ninja - A great 2D stealth game which does a great job balancing the feeling of being ninja that's still a vulnerable human.
Metro 2033 - A very atmospheric post-apocalyptic shooter.
Warframe - Currently in beta, but its a pretty fun co-op 3rd person shooter where you play as space ninjas.
Trails in the Sky has some of the best writing and most fleshed out world I've seen in a RPG. Now coming to Steam Winter 2013. Sequel confirmed Summer 2014