My recommendation is Dead Space. That game isn't just one of the countless survival horrors - developers showed a deep love for detail about the environment of Ishimura... this, united to the unnevering music and the main enemy of the franchise, the Necromorphs, in their various (and hideous) forms, can give you a mix of claustrophobia and paranoia. Especially because the cutscenes are actually real-time events that happen in place - and this mean that you have to stay CONSTANTLY staying vigilant, Necromorphs can crawl out from the various corners of Ishimura and attack you at any time.

SOMA. When I played this game a while ago, I immediately put it on my favorite games list. the setting, the story, the way the plot is discovered. The narrative is pure horror.(thanks google translatexd)

Since we're talking about good and old I can recommend Clive Barker's Undying. The atmoshpere is really good, and if you've read any of CB books you know how it's going to be.

Just try DARKWOOD! Your life will never be the same. A sleepless night is guaranteed.

CARRION should be worth a try - especially as a free demo is available to test the quality and handling.

The game mechanics is quite interesting and strategy is varying ... both in a way keeping the player engaged.
It made me experimenting a lot before getting how to proceed - and is on my wishlist concerning the full game.

So I will buy the full game when I have played the games I have not even tried ...
and I am happy that Carrion is playable under GNU/Linux without crashes!
Unfortunately there is a rising percentage of games failing with controller support
or even showing severe stability issues ...
So Carrion is really worth a recommendation!

Either Bioshock or System Shock 2 (which frankly if you go back and play after Bioshock you realize how much Bioshock was essentially a remake of it).

Trapped in a ravaged underwater city, where only a thick layer of glass and metal protect you from the crushing dark and freezing waters surrounding the necropolis, surrounded by mutants, strange little girls and their monstrous protectors, you find your life entwined with unseen observers. Guided by these observers, you make your way to the heart of darkness while subjugating your body and soul to the same evil that created the lurking terrors that seek your destruction. Darkness and isolation--even ghosts--all hammer at your sanity.

With a superb sound design including audio diaries detailing the denizen's downfall, superb lighting, and a world both alien and familiar at the same time, Bioshock is a superb haunted house ride.

Just don't think about the final boss battle too much....

Alien Isolation is scary, sometimes alone, sometime with someone,,

but the alien make us trembling and always careful to take a step...

If it can be any horror game, regardless of its availability for PC, respectively its availability here on GOG, then:

Eternal Darkness: Sanity’s Requiem for the GameCube.

If it needs to be here on GOG to count, then:

Realms of the Haunting.

I know, many won't count that as a horror game in the truest sense of the word, but I always felt it to be pretty "spooky".

Resident Evil 0-3 and CODE: Veronica. Also Dino Crisis 1. Some of my favorite games.

Your heart is pumping with fear, only adrenaline keeps you going, the radar doesn't detect any life form but you know it only takes a split second for the creature to get to you and if it does it means death or an even worse fate...

...you try to calm you breath desperately to avoid catching the Xenomorph's attention, you keep moving through the dark corridor of the Sevastopol station on your way to restore the power and only the flickering emergency lights guide your path, only 100 meters more... 50 meters...

...suddenly you hear a screech on your back and a chill runs down your spine, you freeze and slowly turn around only to see it's tail disappearing in a corner, the Alien can sense you are close, you have to be as fast and silent as you have never been in you life...

...just as the locker door closes it comes running down the hall and stops near your hideout, you are shaking and almost eye to eye with the acid drooling nightmare, it goes on it's way and you live...

...for now.

Alien: Isolation is a true sci-fi horror masterpiece, the shear tension it creates on you only with the sound, the atmosphere and the constant menace of the Alien being around is uncomparable for me with any other horror game i have played, it really puts you inside the game.

I really love science-fiction, if i win one of the bundles i'm looking forward to play Observer: System Redux.

I recommend Grim Fandango Remastered.

F.E.A.R. series is amazing!

Since "Outlast" has already been mentioned (and I was too scared to complete it), I'd have to go with "Remothered: Tormented Fathers". When I found this game here in 2018, I'd just expected it to be like the classic survival horror games ( "Resident Evil", "Silent Hill" etc...) that I played back in the day.

Instead, it was this heart-poundingly ultra-suspenseful stealth game set inside a creepy 1970s-style mansion. Even with the graphics settings and resolution scaler turned down to almost Playstation One quality (since I was using integrated graphics), this game still managed to leave me feeling genuinely shaken and terrified on numerous occasions.

There were nights where I'd sit down to play it, only to find myself spending most of the time cowering in a hiding place unsure whether it was safe to emerge. And even the hiding places are scary, thanks to the sound design, the restricted view and the way the perspective shifts to first-person.

But, although the ultra-suspenseful gameplay is the main source of horror here, the atmosphere of the game is very reminiscent of an old horror movie from the 1970s and the characters/story can also be surprisingly disturbing too.

Yes, it could be because it was the first "run and hide" style horror game I ever played or because I'd initially expected it to be a different type of horror game, but its second only to "Outlast" in terms of the scariest games I've ever played.

The 7th Guest is a must for those who want horror with their puzzles. Or is it puzzles with their horror?

Much has been said about Amnesia: the Dark Descent, and it's well-deserved, but I'll never forget Penumbra: Overture. That game changed me.