The hall with the piano that plays itself. There's a scene where after that room collapses in on itself, I was getting ready to leave, and I heard this growl coming from the other end of the hall. I instinctively go down the opposite end of the hall to avoid getting eating by a monster, and without realizing it I was heading to the room which caved in. Then suddenly, a loud growl comes from behind, and ofcourse I couldn't run into the room because it's blocked with huge boulders in the way, so as I slowly turned around, and a grunt is standing right infront of me, before it fades into a mist of smoke. Never has a game made me scream then whimper like that scene did xD
There's tons of other parts, but way too many to list. The Torture Chambers were definitely the most unnerving thing I've ever experienced. That sawing sound was horrifying, and entering the room with the Brazen Bull filled me with dread.