I like the old silent German Expressionist films of the 20's, such as Der Golem, The Cabinet of Dr Caligari and Nosferatu. I also like the Hammer Horror films of the 60's.
The Grudge, it freaks me out. I think the fact that you see the "thing" coming after you is scary. I have a couple more, however, they are lame.
DAWN of the DEAD is my all time favorite horror movie. Have seen many others but this one i liked the most.