This is a hard one for me, I can't just give ONE movie that credit. I'll give you my top 5.
1.) The Exorcist- The movie is not only got some creep factor, obviously scary but it's not for Regan it's the acting in it and how amazing the mood and cinematography was.
2.) Texas Chainsaw Massacre (73)- It's an indie classic! It almost felt like a snuff film, so well crafted. The violence feels real and the B-Roll of the house is creepy as fuck!
3.) Return of the Living Dead- That's on my top 5 favorite movies, it's just fucking fun!
4.) John Carpenter's The Thing- Between the acting, great special effects that hold up, amazing gore, it's just a damn good movie.
5.) A Nightmare on Elm Street- That one speaks for itself. It's scary, atmospheric, just well done!