I don't have favorite movie, more like a favorite style. I prefer subtle horror that makes my brain think, more than ones full of gore and jump scares. "Signs", despite being full of all kinds of plot holes, had some genuinely creepy moments, like when he sees the foot in the corn field, or the alien on the roof. The birthday party scene really got to me, because around 20 years ago I had a dream that was identical to that scene. That dream was so intense it stuck in my memory, and when I saw that scene I freaked because the similarities were uncanny.
That being said, I do enjoy an occasional gorefest. I really want to see The Green Inferno. It looks like a remake of Cannibal Holocaust so it's bound to be all kinds of crazy.