G
Titanic..
The Exorcist - I was stationed in Georgia when it came out. Lots of "old world" superstitious people live in the south. When the movie started, the place was packed. By the time it was 2/3 finished the theater was half-full, and by the time the movie had ended there were maybe 12 people left in the theater.
The rest had run for their lives...LOL.
Runner up: The Omen (the original, not the crappy remake).