You can’t beat the original *Night of the Living Dead *for horror. Lots of gore, but somehow in black and white it is even scarier!
Also, while not strictly horror, *Play Misty For Me *is the one movie that scared me more than any other. With absolutely nothing supernatural about it, there is no reason NOT to believe that it could really happen to you!
I cannot recommend The Woman in Black enough. Not only one of the best horror movies I’ve ever seen, but one of the better movies generally I’ve seen in the past year or so.
I streamed about half of the original Thai Shutter over Netflix and it just wasn’t working for me (the movie, that is, not the stream itself). I got bored and gave up.
Monster House. Brrrrrrrr.