During my first play through the game back in 2002, the scariest moment for me was when I encountered my first Crimson Head. It was the very first zombie you encounter (first north corridor from the first floor dining room). Was playing as Chris and had took my time progressing so it had become a Crimson Head before the one found on the west wing's second floor corridor (the corridor with the 3 body length mirrors).
Although I read the instructions on disposal of dead bodies, I'd assumed it was pertaining to the three dead bodies you find throughout the mansion (first being in the west wing's south stairway corridor, second being the the north stairway corridor, and third being in the basement's kitchen in front of the elevator). I also assumed they'd just become zombies so it scared the **** out of when the first zombie I killed sprung back up and came after me as a Crimson Head.
The moment that made me jump the hardest was definitely the moment that stuck with me the longest after my first play through; the moment during the mansion revisit when the camera shifts with the Hunter jumping in front of you in the first north corridor from the first floor dining room. You can only experience it if you enter that corridor from the kitchen's basement rather than the other 3 doors. You also can't have entered the corridor the Hunter jumps out from or you'll just find the zombies (or Crimson Heads) that came through the windows in the first visit.