If you haven't played Dear Esther or Conscientious Objector, stop reading this and do so immediately. Not just because these two games by thechineseroom are tremendously interesting experiments in their own right, but because they're honestly quite a bit better than thechineseroom's latest attempt, Korsakovia.
Where DE and CO bent the rules of what first-person gaming can be and what emotions it can evoke -- Dear Esther is utterly without challenge or conflict, and Conscientious Objector is entirely about making the player feel like dirt -- Korsakovia feels weirdly familiar. You run away from bad dudes in a linear, darkly-lit environment while navigating some fairly difficult platforming sections and a few jumping puzzles. Whether that sounds good or bad is up to you.
Personally, Korsakovia's basic gameplay makes my least favorite game from thechineseroom yet, but its dedication to merging its creepy atmosphere with a wildly interesting story keeps me coming back. How interesting, you ask? Consider your role: you play a mental patient who has gouged his own eyes out.
Granted, I haven't actually finished it yet. It's way, way too frigging hard to figure out where you need to go at any given time -- after my second time getting completely lost, I got so irritated I shut the game off. Still, though, the story and atmosphere alone are worth the price of entry (which is free, assuming you own Half-Life 2: Episode Two). Get it here.