I'm going with the first one. It was the first one I ever saw when I was little and you didn't know who the killer was (at least I didn't). Like Brenda with the running around in the rain following the "Help Me!" voice. Ned seeing the figure up in the cabin before he gets it. All the bathroom stuff with someone hiding in the showers - I thought that was creepy. Part 2 gets my second vote, then 4.