The Shining was just pure fvcking brilliance. I'd say it is the scariest movie I have ever seen. It's the only movie that really ever gives me chills.
Evil Dead was the scariest movie I had seen when I was very young. (saw it after my parents got a VCR when I was about 6 or 7)
Alien & Aliens were pretty damn scary when I was little.
Currently, I don't really think any recent movies are really that "scary", however, Audition and Gozu both had some interesting momments. Also, the movie "Spoorloos" was pretty evil.
I'll agree that "slasher" or "gore" movies aren't usually scary at all, but that's not gonna stop me from loving B horror. There are lots of amusing flicks out there, many are worth at the very least a good laugh. 🙂
Also, Shadowknight .... In the Mouth of Madness is awesome.