earliest was exorcist. that was a trip. then jaws. the omen/damien stuff gave a chill or two. as I got older nothing really scared me when it came to horror. I laugh at it, no joke. the last horror movie I watched that gave me a good chuckle, was terrifier 2.
I'll go with the exorcist.
saw it when it came out as well, it was a good one. rats, so many rats.