I don't know of this is Halloweeney or not, but the movie that has always scared the sh*t out of me is the Donald Sutherland "Invasion Of The Body Snatchers".
Of course the embryonic slimy unfinished pod people are just nasty as hell, but after the movie was over the sense of paranoia and dread stayed with me. Ugh, I still get shivers.
And it certainly didn't help that they get you while you sleep.
And then there is that final shot......
Anyway, I only have three more words to say:
hobo and dog
....but the world goes 'round