This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Angel Heart
Finding Margret's heart near her body, with the cavity of where the heart used to be.
The last 30 seconds of the film.
Pretty much the rest of it too. Like Eraserhead, the entire film is shot, soundmixed and scored to evoke the feel of a nightmare, with muffled, distant sounds, sudden flashes of seemingly irrelevant images, and moments appearing out-of-sequence. Harry himself has a number of nightmares (later revealed to be where his mind goes when he's under Satan's control), which feature copious amounts of blood.