The scariest thing i have had in a game was in Bioshock. I was following a list of the power to the people stations and i came to the one in fort frolic that is hidden. Throughout the level there are these statues covered in cement
(These are not the ones that bother me) When you go into this room where there is a bar. The power to the people station is in this closed room in a basement. In order to go in that basement you need to push this button that unlocks the basement door. (i forgot to mention this ENTIRE room is filled with the statues like everywhere seriously)When you open the door you see this long stair case at lights flashing at the bottom so you know that is the last place i wanted to go. Down in the basement there is this statue cemented into a chair. The power to the people is at the end of the room. So i activate it you know upgrade my shotgun i turn around and see that the statue in the chair is gone and there is this new statue cemented right behind be. In a split second after pointing the gun at it the statue attacks i kill it then RUN THE HELL OUT OF THERE.
when i come back up the stair the entire room is missing statues like there 15 that were there are gone. I get out of there and all these other statues are missing. I turn around somewhere and 5 statues are cemented behind me and attack me. The entire level is like this and it became a nightmare half the time i had my back to the wall.
here is a video of this bar that its in