- Choking Hands. These buggers are little enough to be immune to bullet spam, appear suddenly from unexpected places, and when they choke you, you cannot do anything to them except try to pull them off (with your vision darkening, sounds of gasping and your health quickly going down). If you can fight them without getting the heebie-jeebies, you have nerves of steel. If you can kill one with a single pitchfork blow, you are both utterly fearless and really masterful.
- The Bone Leech in the sequel, which is to this game what the facehugger is to Aliens vs. Predator: Extinction - it should be very obvious how Monolith wound up making Alien Vs. Predator 2. It gets worse when you see the Soul Drudges, Drudge Lords and Drudge Priests are the results of what happens to the victims. The fact that the Lord is a Demonic Spider and the Priest is a Boss in Mook Clothing that can spawn more Leeches doesn't help.
- If you don't Read the Freaking Manual, it isn't obvious how to remove bone leeches and the like. While this is the case, walking into any dim area or murky pool is terrifying, as at any time a monstrous creature might jump onto you, completely filling the game screen, and (slowly) kill you.
- Hell, there are several noises, visions and general stuff that manage to make the game pretty damn scary. Of note is the apparition on the window at the end of "Rest For The Wicked", a ton of the shit in "The Haunting" (an eerily large, quiet and dark mansion with several vent holes out of which both Spiders and Hands come crawling, a hedgemaze way creepier than the one in The Shining, and secret passageways filled with Phantasms, and that's not to mention the slaughterhouse - the first building you find in the level and only access much later; it's full of hanging mutilated bodies, disturbingly well-placed blood, and Hands - and the goddamn basement). That, and the sense of foreboding you get in any silent level. To boot, if you play the game with CD music on, "The Haunting" will have easily the creepiest ambient music in the game.
- The Phantasms themselves, thanks to their alarming appearance (imagine a white mini-Grim Reaper with a Slasher Smile) and the way they scream bloody murder non-stop, as well as their prospensity for taking you by surprise. As one reviewer puts it, the Phantasms were probably voiced by a guy whose balls were put in a rat trap, so much misery and hopelessness is in their screams.
- The Game Mod Death Wish for Blood manages to up the creepy. Highlights include the screeching, human-headed spider scurrying around on "What Lies Beneath" (the entire stage, in fact, is an excellent Shout-Out to John Carpenter's version of The Thing (1982)), and the two Silent Hill-inspired levels.
- On the second level of the first game, you can skip the level exit and go straight into the train tunnel - which results into you walking a long dark hallway in pure silence for a couple of minutes, only to get hit by a coming train. This was years before a similar technique was used in games like Silent Hill or SCP-087.
Nightmare Fuel / Blood
Though the game uses its own horror as a constant point for comedy, some things are still terrifying regardless. Caleb is a wisecracking, cackling Villain Protagonist, but that doesn't really seep enough into some people to make these parts very tolerable.