We all know that GMOD Horror maps aren't exactly regarded to high standard... and for good reasons. Source is a difficult engine to get a hold of and I'm not just talking about Hammer. This results on most horror maps being almost entirely recycled to the point that if the most basic change to the formula ganders high praise, even if it is not entirely deserved (I'm talking here about switching from 2d png jumpscares to 3d jumpscares, it's literally the same thing but slightly less awful).

Now, what are the sins of GMOD Horror mapping? Well, in my opinion:

• Mazes. Don't get me wrong, mazes can enhance a horror map, but, as they are most frequently implemented... mazes are inserted into a map solely to put more jumpscares or make the map feel longer.
  
• Obnoxious jumpscares with zero to no buildup. You can make the jumpscare as loud, as grimy, as unexpected and as high quality (visually) as you want, this won't make them any better. A png jumpscare with good buildup and clever sound usage is not only scarier but also feels much less onoxious than an out of nowhere ghoul that screams real loud.
  
• Boring and uninteresting environment. What's wrong, love? You haven't touched your 54th horror map that takes place in a boring abandoned dark concrete building. Creativity is key. If you do not make the location visually interesting or unique, the player will most likely will get bored before they reach even the halfway point of your map. The worst offenders of this include: Generic abandoned concrete buildings, Generic wooden manors, Basements, Schools, Slender forests, Evil laboratories and of course The Backrooms. What I would love to see is more unique locations for a horror scenario, like a submarine, a residental complexes, an Industrial factory, a cargo ship, a plane, an airport, an underwater facility, a space station, an alien planet, Local villages, Caves, Non-abandoned buildings, Offices, No Man's Land, etc. Something, anything to keep the player interested. A good horror game isn't just scary, it is interesting to immerse yourself in. If the player isn't scared, they just won't play the map further.
  
• Combat. Fighting zombies isn't scary by itself. Make it feel scary.
  
• Puzzles. Don't get me wrong, puzzles can enhance the horror map when done right... if done wrong, however, will do the exact opposite. Offenders include Shape Puzzles and Jigsaw puzzles. These kind of puzzles stagnate the whole map at best and ruin the atmosphere at worst.
  
• Huge spaces or Agoraphobia. This is commonly found of "first map" horror maps, where the mappers only recently learned how to use Hammer. I think it's pretty obvious that open spaces are not scary. So, unless you're using these open spaces to enhance the horror, they don't add anything to the map and only make it slightly more annoying to play.
  
• Player death. Either by hazards, enemies or jumpscares. It breaks immersion and may frustrate the player especially if it's a kill trigger.

The most important thing is for the map to be fun and interesting.

With that out of the way, let me introduce you to my personal collection of GMOD Horror maps. I personally found them worthy of being called "good" horror maps, better than the slop that usually reaches 5 stars on the workshop. And they should be held as an example on how TO make a good horror map.
Does that mean that I think that other Horror maps that are not in this collection... are banal slop that doesn't deserve attention? Probably.
I do have to clarify that while I think these maps are good, they are not perfect. They have flaws and some even have one or two aformentioned "sins" that I mentioned. So learn to see what is good about the maps and what is bad.

Note: I will not be adding joke "horror" maps into collection as they aren't focused on being a horror map and more like a joke, even if some of them are quite funny and fun. Also co-op only maps, for obvious reasons.

Feel free to suggest maps that you think deserve the spotlight in the comments. That is, if the map even gets out of the 0 star hell in the first place, Gmod community needs more NSFW goonslop, I suppose.

Edit: Thanks for 4 stars! Didn't think it would get that far, huh? Again, thanks a lot, this collection was made of love for the community and not of hatred. Have a spectacular day!

Edit2 [10.07.25]: This collection isn't abandoned, there just weren't many good horror maps that have been released in the past year.