It's kinda tough to choose just one. But the scene that stands out for nightmare fuel is the one of the nun painting in Conjuring 2. Just a whole lotta nope.
Never saw conjuring so i cant say much about it.
But as for insidious it was not very scary. It had some good jump scares but once i saw Darth Maul as the bad guy it quickly morphed into a comedy. I kept yelling, "use the force!" and "don't go in there Obi-one!"
It absolutely ruined it for me with that design. After his face reveal even the jump scares seemed pathetic.
Not any of that Jason Saw Chainsaw Massacre ect. shit.
The Shineing
The Thing
Bram Stokers: Dracula.
Event Horizon
New Stuff has a hard time living up to the old greats.