Night of the Living Dead.
My brother took me to see it back when I was around 10. I remember my mother cursing my brother out for taking me to see it.
This one theater used to show it every Halloween.
I still get creeped out in cemeteries. The opening scenes, where the one zombie is walking around the cemetery in the distance , and the brother telling his sister "Hes coming to get you Barbara"did it to me.