This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Ghostbusters
The library scene isn't exactly the scariest scene in a movie, but it can really catch you off guard if you haven't seen it before.
The following involving the demon dogs Zuul and Vinz Clortho. First, we get Dana being grabbed by Zuul note three demonic arms emerge from her chair proceeding to hold her down as the door opens to Zuul, the chair zooms towards the door and shuts when she is in the same room as the demon dog , which leads to her possession; then we get Louis chased out of his own party by Clortho, who is cornered by the monster. Then, we see Dana as she's under Zuul's influence. It's sexy to male audiences at first, but then Zuul takes over and she starts hovering above the bed and makes beastly noises. Meanwhile, Clortho, while possessing Louis, searches for Zuul, and when a cabbie makes a remark, Clortho flashes an intense, intimidating glare.
Ray and Winston's talk about the apocalypse.
Winston: Do you remember something in the Bible about the last days, when the dead would rise from the grave?
Ray: I remember Revelations 7:12 note it's actually 6:12. "And I looked as he opened the 6th seal, and behold, there was a great earthquake. And the sun became as black as sack cloth, and the moon became as blood."
Winston: "And the seas boiled and the skies fell."
Ray: Judgment Day.
Winston: Judgment Day.
Ray: Every religion has its myth about the end of the world.
Winston: Myth? Ray, has it ever occurred to you that maybe the reason we've been so busy lately is 'cause the dead have been rising from the grave?
"How about some music?"
Egon's descriptions of Ivo Shandor, the architect of Dana's apartment building, who designed it to have secret passages leading to the roof, which served as an alter for his ominous Gozer cult. Egon also mentions that Shandor was a doctor who performed a lot of "unnecessary surgery."
The way Egon smirks while describing Shandor's "unnecessary surgeries." Egon isn't especially good at reassuring smiles in the first place, but in this situation it just looks like he's enjoying Shandor's shenanigans entirely too much.
The darkroom scene in Ghostbusters 2: A claustrophobic room lit with red light (naturally), the doors silently sealed shut without their knowledge, peering intensely at photographs of a possessed painting, which suddenly all catch on fire at once. Not for the pyrophobic and/or claustrophobic.
Made worse once you realize that Ghostbusters 2 is much more of a kid's film than the first movie (no one smokes except for Ray and even then he's only seen chewing on the end of an unlit pipe or cigar or holding one (he never has a cigarette), less swearing, far less sexual themes) and they still felt the need to include a scene where two of our main characters nearly die by being burned alive. The utter terror in Ray and Egon's voices as they start to panic and scream for Winston while banging on the door before resolving to run into the bathroom (though Ray questions what good that'll do)... What Do You Mean, It's for Kids?
The "everything goes to hell" scene from the second film, featuring an array of ghouls a lot more intimidating than anything else seen in the series - including a spider-like thing with four arms and fangs that chases a bunch of people out of a store, a fur coat coming back to live as a rabid four headed snarling beast that scurries down the sidewalk, and culminating in an enormous monster reaching over the Washington Square Arch and looming over a crowd of screaming people.
The living fur coat and the return of the Titanic in the second movie.
The extremely spooky By the Lights of Their Eyes scene of Janosz alone in the darkened apartment corridor. His eyes don't just glow, they shine like high beams.
The pink slime in the second movie is both this and Nausea Fuel at the same time. The way it drips and moves can cause some sense of revulsion, and the fact that it's the physical incarnation of human negativity can make it create all kinds of horror, like the above mentioned living fur coat, the return of the Titanic, the rise of many spirits and demons, and (judging from the calls the police were receiving) even make dinosaur skeletons and a park bench come alive and be scary.
Not to mention the fact that Ray, Egon and Winston almost drowned in it.
And when they got out of it, they were, as Winston puts it, ready to kill each other for absolutely no reason. The slime doesn't just conjure spirits—it makes people Brainwashed and Crazy. What would happen if some of that gunk crept up to the surface?
The decapitated heads on spikes appearing while Winston, Egon, and Ray are searching the abandoned pneumatic transit tunnels. It comes right the fuck out of nowhere and stops almost as quickly as it began.
There is something extremely unsettling about yelling "Hey!" to hear the resulting echo, then silence.
When baby Oscar is shown standing on the ledge of Dana's apartment building, looking down at a couple hundred foot drop, is frightening to anyone, not just mothers. Just goes to show how much Dana loves him, she willingly climbs out onto the ledge to save him.
Add to that Janosz flying towards them as a spectral nanny who comes to kidnap Oscar. There's even an up close look at his face where his eyes are glowing red and he has a demonic grin on his face.
Despite being a comedy at its heart, there are still plenty of genuinely scary moments in the movies. The new game has its moments as well. In the movies, bonus points go to the phantom librarian, the zombie cabdriver, the Marshmallow Man's Uncanny Valley ramped up when it's angry, the Scoleri brothers, the heads on spikes in the Sinister Subway, the museum boss dressed as a phantom nanny who spirits Oscar away, Vigo's eyes shifting at the beginning of No. 2...