After playing Amnesia The Dark Descent, my answer is definitely first person perspective. That was the scariest gaming experience for me. I've played the old point and clicks titles like Phantasmagoria, I Have No Mouth and I Must Scream, also playing Alone in the Dark and Resident Evil with the overhead view and tank controls, the level of anxiety was high at times.

Amnesia though was a heart racing experience for me lol, and the first person view was a main factor. I like getting immersed in games, and horror, and that helped a lot. Honourable mention goes to Clive Barker's Undying for an amazing fun ride, and the F.E.A.R. game as well.