"The Exorcist" (1973)

[jaragon]

William Friedkin's film of William Peter Blatty's novel still works because Friedkin takes his time developing a very real world before the horror begins.   In the excellent behind the scenes documentary in the last blu ray edition of the film  we see that most of the shocking imagery was created by practical effects.  The character are seeing the real thing live as it's happening- which makes it more convincing if it they had used modern CGI.  

 

[cinemaspeak59]

One of the best & scariest movie ever.