Cold Fear/YMMV

Anticlimax Boss: Anishenko. Kamsky, during the "second round" is one if you know what to do.
Demonic Spiders: The crawlers, who are wall masters, can take a half dozen shells of buckshot at point blank range, and will use the ventilation shafts to get behind you and sneak up on you. As an extra little 'fuck you', they cannot be looted for health or ammo after they have (finally) been killed.
Goddamn Bats: The parasite forms often appear in groups, present only a tiny target, curl up into a ball and roll away after being hit, and to top it all off, they'll often pop up out of the neck hole of a recently defeated zombie.
High Octane Nightmare Fuel: Let's see: a dark, unsafe location far away from the civilized world? Check. Zombies, parasites and other grotesque freaks all over the place, some of which can make themself invisible at will? Check. The scrapped material however sells it by showing a huge number of really nightmarish scrapped models for both the exocells and mutants, including a mutated whale, mutated hounds and what seems to be a mutated zombie seal.
Paranoia Fuel: Creepy not-quite-dead guys are scattered all throughout the game; their skin is very pale and they are largely unmoving, but their eyes are wide open and their jaws are slack, and their heads bob slowly up and down. Though they are not in any way a threat, you will likely find yourself blowing off the heads of every. Single. One.
- It is later revealed in one of the discarded notes that these guys are former hosts to parasites that have used them up, eaten their brains, and moved on to find a new host.
- The elevetor of the Scientific Module has three huge "asymetrical specimens" in jars of yellow liquid. They're still breathing. And yes, you'll feel like they're about to jump at you at any time. Only one of them does.
That One Boss: Near the end of the game Tom fights against one of the invisible specimens inside the drilling station's explosives storage room. There are explosive barrels EVERYWHERE. Basically, you have to shoot something that is completely invisible, moves very quickly and has loads of health, and if you miss a single shot you'll most likely hit a barrel and blow yourself up. And if you run away, the stupid specimen will set off the explosives and kill you before you can leave.
- Or, you can try to get attacked, grapple him and succesfully score a Critical Hit, which kills him istantly without setting the explosives.