No film has ever been scarier to me than the remake of Invasion of the Body Snatchers starring Donald Sutherland. Granted I was only 4 years old when I saw it (I can't remember how that happened) but it's still a scary film. This end scene in particular has stayed with me. It wasn't just the horrific pose and scream, nor the idea of being surrounded by evil aliens, but - even at that age - I found the notion of being the only human left on Earth scary. The fear, the loneliness, the total isolation... terrifying.