I was entering to mention Prince of Darkness, but it's been done. Many Carpenter movies would qualify. All are enjoyable, even when terrible and cheesy. But Prince of Darkness had terrified me. To be honest, so did Raimy's Evil Dead.
I love the old universal edgar poe movies, with Vincent Price. And the Hammer Cushing Lee stuff.
And Balaguero's [Rec]. Not the sequel, not the remake.
I like Argento movies, but from a certain distance. Even though I appreciate the formal spectacle, I don't really manage to "enter" them. Except the Stendhal Syndrome (fittingly).
Anmd I completely adore Don Coscarelli's Phantasm series.
The rest are obscure movies, but not B. Qualiy stuff such as Darkness, Ravenous, and, yes, The Changeling, or Communion.