The first horror movie I can remember watching is Cujo. I think maybe my parents thought it had cultural value as a Stephen King property. So one day, as we were perusing the shelves of Movie Madness, the tiny video store just a couple blocks away, they let me snag that tape off the shelf.* (There was a prize wheel at the register. I bet I got to spin it. And I bet they were kind enough to give me a prize no matter what. [I believe I was about 8 or 9.])
I was a Beethoven fan then I watched Man's Best Friend and was horrified!