I think the mod Nightmare House deserves a brief mention. How many other good horror mods have there been? I can't think of many at all. Does the new one called Flesh count? I don't find it scray yet because there are some issues with the NPC's and player movement. I also found 3rd person to remove the fear for me. But in Nightmare House, you are all alone with the zomb's and it's actually horror.
RE4 was a good scary game because I felt a need to preserve myself - the enemies were very hazardous and aggressive, especially the chainsaw guy. My very first time playing Half-Life was an absolute shit in the pants because the aliens would appear from thin air and attack from behind. The darkness and the storyline were so freaky and my imagination ran wild while crawling in the vents.














