10. Close Encounters of the Third Kind - "We are not alone."
Spielberg knows how to do an effective tagline and he strikes gold again here by tapping into Close Encounters sense of wide-eyed wonderment and child-like excitement. Its simple but effective and perfectly encapsulates the films central theme. It was rare for a Sci-fi movie about alien contact to not create a sense of danger or panic. These weren't aliens out to kill or conquer us, they were placid beings out merely to make contact. The phrase "we are not alone" helps cultivate this friendly-alien image and reinforces the feelings echoed throughout the movie by Richard Dreyfuss' arch-believer Ron Neary.