Welcome to the ZDoom Forums!

I understand that for some peoples Doom 3 is probably not as scary as one would think,while there are others who did find that game scary.

Doom 3 was quite impressive with its lighting and shadow effects back when it came out and it deviated from the more fast paced action of the originals,in favors of a more slower paced and darker game with tense atmosphere and jumpscare moments.

I am here to talk about what i actually found scary/tense about the game,there are actually 6 enemies that make me uneasy when im eventually confronted by them.
I have put these enemies that fit in one or either of those 2 categories, 1-enemies that move fast and 2-enemies that have a more menacing sounds.

The Maggot - http://doomwiki.org/wiki/Maggot : These guys are technically less resistant than Imps and dont throw fireball,but because they are faster and more agressive in their movements,plus their orange glowy eyes,they make me nervous when i see one coming toward me with fast pace.

The Commando (tentacle version) - http://doomwiki.org/wiki/Commando_(Doom_3) : Like the Maggot,this guy also charge at you very quickly,sometime even jumping forward toward you with his tentacle,when i hear them say -YOU- and then followed by their footstep sounds getting closer and closer,it does make me frightened.

Ticks and Trites (spiders) - http://doomwiki.org/wiki/Tick_(Doom_3) http://doomwiki.org/wiki/Trite : Ok sure,they can be quite easy to dispatch,but i still dont like being cornered in a room or hallways with a bunch of them.

Cherub (half babies,half insect) - http://doomwiki.org/wiki/Cherub : I dont like the sounds they make and they can be sometime a bit quite difficult to kill if you dont have the right weapons or if you have difficulty aiming at them,because they are small,fast and can lunge at you once they get close enough.

Hell Knight - http://doomwiki.org/wiki/Hell_Knight_(Doom_3) : Now the reason why these guys make me uneasy is not because they are bigger and tougher version of the imps,but because of the heavy footstep sounds they make,it make the Hellknight sound more menacing and i do get nervous when i hear them in the distance with the sounds becoming louder and louder as they get closer.

Bruiser - http://doomwiki.org/wiki/Bruiser : These guys are basically like the Hellknight but i find the sounds they make are even more terrifying for me,their footsteps sound even more heavier and metallic,the growling sound they make and their projectiles are more difficult to dodge if you are in a more tight location,especially since they can spam their projectiles faster and more often than an imp or Hellknight.

Doom 3 wasn't scary for me.Maybe bc I kept in mind it was only a game?Didn't help much when someone called the monsters "poor little f***kers" either.The comment made me lol..a lot.

Doom 3 achieved something which only Freddy Krueger and The Mist could: it scared me shitless! It's a bit shame that the world had to wait more than 10 years for a sequel...but it was totall worth it!!!
Soooo, which were the scarriest aspect of Doom 3? That's an easy one.

Red visions - Combined with the feeling of being lost and everyone is dead, these were one of the best nightmare fuels. To this day I never really know what these red visions are for. The most plausible explaination is that the red visions are Hell's failed attempts to turn you into a zombie. At the very first, you can see yourself in the mirror being zombified. Red visions were extremely spooky with all its effects (mouse sensitivity drops, scarry voices and whispering).

The voices from the walls - Needless to say, this is something I haven't met in games, and every time I've heard whispering, talking, or evil laughter, it sent chills up and down my spine! The best was obviously the "They took my baby" scene.

Those meaty stuff comin' out from behind the walls. I haven't the foggiest idea what is it, but looks damn disgusting and is something which wasn't really witnessed before Doom 3.

Many jumpscares involving metal lids falling, enemies crawlin' out of the walls and floors, or stuff collapsing underneath you.

Cherubs were really scarry ass monsters, I haven't expected such things to see! Yes, the Chee was a very clever invention of ID Software! Trites, on the other hand, might seemed scarry at first, but once you realize they can be smashed easily, they quickly lose their appeal.

The Hell level as it is, damn scarry and really makes you refrain from committing any sins! Especially if you think about that the Doom 3's hell is man-made, reality will be much MUCH worse

Sound design was top-notch in Doom 3. There were sounds playing nearly everywhere; regular machinery and computery stuff alongside with hellish ambience really made it feel tense. I remember my first playthrough of Doom 3 back in 2008/'09 i had really poor quality speakers for me and my brothers computer (which we shared), it was pretty slow and could just handle D3 on lowest at ~40 fps (it still looked most realistic than any other game i ever played). Jumpscares always got me and those zombie ambushes from dark corners.
After switching to headphones and replayed Doom 3, the game felt so different when you heard sounds clearly, all ambient sounds and monsters stalking around the corners was pretty damn creepy.
My most memorable moment was in Delta Labs 2A, when you entered the first hall and the "hell influence" happened, made stop playing the game for few days.

I wish that there were more slower paced shooters with sound design like in Doom 3.

The bruisers are horrifying for me. For some reason the screen with human mouth just creeps me out.

I'll confess, I scare cosmically easy and don't do well with even minor horror content, but I never found Doom 3 that scary. Monsters go down easy, and frankly they look more like weird aliens to me rather than demons most of the time. Most of the scares are quick jumpscares or spooky laughs and the like but its not like they're actually out to get you or the like. Anything that can actually harm you is killable.

I dunno, I guess my mind reacts worse to horror content that takes place in a familiar world, rather than some base on Mars entirely disconnected to every aspect of my life.

nobody here even spoke of the pinky cutscene? y'know, the one where it bashes the door in before charging through a big glass pane to begin furiously attacking you..

that was the only thing that really took me by surprise when I played Doom 3 for the very first time. I'd say most of the other enemies I had a pleasure of fighting though!

doom 3 wasn't very scary tbh. i found the lost souls and the cacodemons mildly creepy thats all

Doom 3 was scary for me. Also, I dont dislike it - it just something little bit different.