I queued up to see Jaws on it's release in a cinema on the Bristol Road,Birmingham , it was packed.The reaction to some memorable scenes was unbelievable and hysteria ruled.I had to down a considerable amount of Davenports afterwards to regain equilibrium.
"Good people drink good beer" Hunter S Thompson
I know that Deliverance isn't classed as a horror film, but it still creeps me out more than a genuine frightener such as (say) The Descent.
Forgot to mention The Fog which is quite scary.
And forgot about Manhunter, which was a sequel to Silence of the Lambs but filmed first and remade 16 years later under its original title of the inferior Red Dragon.