I'd say Max Payne is pretty damn dark throughout the entire game.
Apart from Max's sarcastic one-liners and the awesome gunplay, the game always gave me a great feeling of... dread or something, I don't know how to describe it.

Legacy of Kain.

Gabriel Knight - 60% off for the next 2.5 hours. GET THEM.

Arcanum. The industrialisation wasn't pretty in our world. Just see what happens when you throw "sub-humans" into the mix.

This game explores some of the darkest corners I've seen in video games. It's not a childish gorn compilation for adolescent idiots like Manhunt, but a proper, very well written setting that appears fine on the top, but horrible truth is found once you scratch the surface.

And it is a very good game.
Yeah, probably the darkest and best out there.

No one said Silent Hill II yet?

You forgot Vampire The Masquerade: Redemption, it's pretty dark, too.

There are some high quality mods for Neverwinter Nights with dark stories and setting, available for free if you got the base game, like NW Vault is loading a bit slow at the moment, so I don't have time to fill in the links, I might add them later).

I haven't played through Vagrant Story (PS One) but its story and setting also seem to be quite dark. And maybe Enclave, although it's less personal than the other games, it just has a darker atmosphere. Regarding the atmosphere, Arx Fatalis and Gothic might count, too (their setting isn't exactly cheerful, although it's not that bleak or horrifying either, compared to some of the above).

- Limbo. Pretty self-evident, really.
- Time Fcuk (yes, it's spelled that way). An oddball of a platformer with a mindfuck of a story. Don't trust Steven.
- To some extent, Planescape: Torment. This one should be pretty famous already, but if you haven't played it, you should do yourself a favour.
- Arguably, Dear Esther. The story is told through sections of monologue, there are plenty of metaphors and allusions and stuff. It's left up to the player to figure it out, so good luck analyzing all of it.
- The beginning of Fahrenheit/Indigo Prophecy. One of the playable characters ends up in a predicament with no obvious way out while most of the others try to catch him and you're not really sure who you should be rooting for. Unfortunately the story takes some really weird turns about halfway through and eventually becomes an unacceptable trainwreck that, in my opinion, solves the original problem about as well as a blockbuster bomb solves the issue of a slightly lopsided doghouse. Not a game I would recommend; just watch a Let's Play or something if you absolutely must know.

It's probably my favorite adventure game of all time. The only unfortunate thing is that it's so short. Even without hint books one should be able to easily finish it within a week end.

It's also a really good example of quality writing. People complain about the surface level inconsistency in the settings, but they literally are hinting at it from the first scene with some of the items.

I think all game writers could learn a thing or two from the quality of the writing.

The Fallout 3 The Pitt DLC.

Personally I find Sanitarium a bit of a hit and miss as an adventure and as a game in general. But it does try at least, albeit it never manages to get to its fullest potential, which is a shame.

But Blood... damn, when I payed it the first time I really felt squemish, especially when I lit up a couple of enemies. Sadly the sequal is utter crap.

Wow quite a selection. I guess the definition of dark is highly subjecitve. Another dark game that came to my mind is Kingpin. At least it was marked as being overly dark and violent but in the end all that really stood out were the excellent graphics and the suprisingly decent multiplayer. I always wrote off Legacy of Kain as being console stuff. Does it take itself serious then? Hmm I wonder why the first entry to the series is not available on gog. I'm not confident with jumping into the middle of things.

Never played Manhunt but does it feature more then violence and general wrongness? This sounds quite like the thing that could hit my darkness nerve. Will definitly check it out. I bought the witcher 1 back when the enhanced edition hit the shelves but it didn't hook me enough so I haven't 'found the time' to go back to this. I heard the second installment is quite good but then again I'm not starting the series on part two.

I've played planescape and all baldurs gates of course... Good call nevertheless I should dedicate some time to another planescape run. done This is where subjectivity comes into play. I'm generally not able to play horror games. I forced myself to Doom 3 once but that's how far it goes. It's quite a shame as I really like the setting of both system shocks but I absolutely loathe randomly spawning enemies behind me regardless of how careful I play... I checked MobyGames for this one... console stuff again... Do this games even feature some kind of story? This hits the nail on its head. If I would be more eloquent I would have asked for Lovecraftian games instead. Didn't know Eternal Darkness. Will check it out. Bought them already... Good to know that they are considered to be dark. Never heard of it. Will have a look. I just played the first one back in the days. Apart from being dark and serious it was mainly really really difficult. Only know Postal 2. I fear Postal doesn't take itself serious enough to really count as dark in my opinion. That's no bad thing though. I liked Postal 2 a lot. Really? Modern military 3D-Shooter is as anti-dark as it gets... Done. ;) I've already tried twice to get into it's setting. For some reason I can't take steampunk very serious. All the Zeppelins and Valves kill the immersion for me. Will try Arcanum a third time... Played the Demo back in the time. Didn't get it back then. Will try it soon.

Thanks guys for your suggestions. I guess I overlooked quite some decent entries into the darkness genre. :)

Console stuff?!?! Dude, the games are AWESOME. Also, the first is not available because of licensing issues but it doesn't matter, you can start with Soul Reaver 1 & 2 without missing much.

Manhunt... Well, not sure exactly what you're looking for, but it is a pretty grim and depressing game.

Yes, really. As I said: just trust me on this.

Well, nice to see that old PC Gamer elitism. It wouldn't be a PC gaming forum without it. Shockingly, such a thing as good console games do indeed exist. Demon's Souls and Dark Souls are both great (but not for everyone, Orcish can come in to tell you about how he hates 'em ;P). They both have stories that are somewhat minimalist, but are fleshed out by a lot of lore and putting together the pieces yourself. Demon's Souls is a lot darker and more disturbing than Dark Souls.

On Spec-Ops the Line: You clearly know nothing about the game, then. (Which is good! Go play it! I already accidentally spoiled myself and have yet to play it!