Depending on your age and what you're exposed to, there has to be a movie that absolutely scares the piss out of you. Mine would have to be Pet Cemetery. I saw it when I was young and it's stuck with me ever since.
Hmmm, I think it was Saw 1 - 4. It's so disgusting and all! I nearly piss my pants and scream to death! Sigh, good thing they don't make a 3d out of it! Lol. I'll die because of...something. It was disturbing... And this pirated movie that my friend has called 'Knock Knock' it was hell! It was expose to much! I can't take it! Those memories, disturbing memories... O_o
Grudge was the scariest movie I've ever seen. I still get freaked when I think about it. I remember this scary part in it when there's this girl that has horrifying eyes, they were big and extremely scary. AHHH, I'M THINKING ABOUT IT, AHHHHHHHHHHHHHHHH.
Well, I'm not really into scary movies, so i would have to say it is category 7: the end of the world. Not too scary, but it is the scariest movie i have ever seen