The movie that definitely scared me the most was a poorly written, poorly acted late seventies movie called Prophecy. It deals with mercury poisoning in a wooded area of Maine, which creates monsters, including a hideously ugly mutant bear that goes on the rampage when it's cubs are taken by a do-gooder doctor, and company, trying to prove this was all caused by the local paper company poisoning the environment, as well as the local Native American tribe. From the time I had first seen that mutant bear, as a kid, well into my adulthood (I'm embarrassed to admit), I had lived in fear of that thing when the lights went out at night. I've even had nightmares about it. Later in life, when I saw the movie again, I realized just how cheesy it was, and how the only outstanding monster effect was essentially just the bear puppet head used for closeups (the monster suit was actually pretty phony looking, especially the face, with it's never changing open mouth expression). Still, that horrid mutant bear in my head had always appeared much more real looking, and it was that which had haunted me for years.
_________________
-Bill, otherwise known as Kraichgauer