Paranormal Activity/Nightmare Fuel

The First Movie

Night 20. No. The entire movie.
- The final shot of the possessed Katie sniffing at her boyfriend's corpse before smiling at the camera then twisting her face and letting forth an inhuman shriek as she launches herself at it still haunts this troper's thoughts.
The truly horrible moment is three quarters of the way through when, after it being well established that all hauntings happen at night, a photo cracks. At noon. This is closely followed by Katie's realization when the demon's footprints appear in the powder. Why on earth would they appear anyway? Because the demon wants them to. I'm sorry, were you planning on having peaceful dreams tonight?
- "How come my face is scratched and yours isn't?"
In one alternate ending Katie gets out of bed and stares at Micah for 3 hours straight. Then walks downstairs and starts screaming. Micah runs down, and he screams, and suddenly you hear 3 people screaming. And then Kate comes back up with a knife and slits her throat. Disturbing is putting it mildly.
- Another had Kate staring at Micah, going downstairs, screaming, then killing Micah but instead of slitting her throat when she comes upstairs, she just sits there rocking her body for days, the fast forwarding of her rocking only interrupted to get the viewer er a chance to hear a phone call (answered by the machine) from her friend. She just keeps rocking. It ends with the police coming to investigate. Kate finally comes to for a bit and starts walking towards them, still with the knife in her hand, and they shoot her.
  - On second watch, the "Cop" alternate ending becomes even more terrifying. As the cops enter the house and come up the stairs, the lights in the hall flicker on their own accord. The demon? HE'S CONTROLLING THE ENTIRE HOUSE AS WELL AS KATIE. And then, you see Katie get up confused and disoriented... the demon left her body. And as the cops draw their guns on Katie as she comes with the knife, watch the door in the background. The cops didn't shoot Katie because she was threatening them. The demon SLAMS the bathroom door, and the resulting sound gets a cop to pull the trigger.
The very real portrayal of their relationship breakdown. Whether the demon was real or not, it was clear that Katie was terrified. She begged Micah to stop filming, she begged him not to play its game. What did he do? Completely ignore her and make things worse.
Scariest bit in Paranormal Activity? The bit with the flour on the floor and demon tracks. Funny thing, really, considering most demons are depicted with their feet backwards. As in, it's in the room with them.
Micah is hurled into the camera by the demon. It wasn't really the act itself as much as it was the fucking roar the demon made while doing so.
That last second at the end before the jump scare, when she's looking into the camera and smiling horribly. It can feel as if she is staring right at you, the viewer.
"I think we'll be okay now."
Towards the end of the film, when Micah is all set to leave for a hotel, Katie suddenly claims that she'd rather stay home. Paying close attention, you can tell she's not speaking normally. In fact, she's speaking in much the same way she did on the swing earlier in the film, like someone else is trying to do a convincing impression of a human. If it wasn't obvious already, the slight double-voice you can hear as she says, "I think we'll be okay now," followed by a small smile, should make it very clear that she's possessed. It's subtle, yet still noticeable to the attentive viewer, and so it's absolutely horrifying and makes you realize that whatever hope you may have been holding onto for the characters is best abandoned.
Katie being dragged out of bed and down the hall by her feet is terrifying to watch, especially since the demon had largely stuck to smaller, much less harmful scares up until that point.
The discovery of Katie's photo in the attic.
The scene where Katie and Micah hear the demon thudding up the stairs really, really fast, before suddenly falling silent.
An early jump scare features Katie and Micah hearing a loud BANG from downstairs... but what really makes it terrifying is the demonic howl right before the bang.

The Second Movie

Kristi sitting in her kitchen and suddenly looking up and behind her is tense, because you know something's about to happen. Most viewers aren't going to expect every cabinet and drawer in the kitchen to burst open with a loud bang. It startling beyond belief.
- Kristi trying to cope with a Stepford Smiler attitude immediately after doesn't help.
Kristi's possession. Just... dear god...
If you though Katie being dragged down the hall was scary...hoo boy... Kristi gets not only dragged out of Hunter's room in a similiar manner and latches onto the railing for dear life.... but runs back into Hunter's room only to be dragged away AGAIN, this time down the stairs, through the hall and into the basement after which the door SLAMS shut after her.... just damn.... Later we're even graced with a look at the back of the door showing that she appears to have tried to claw her way out of the basement..
The scene where Ali's asleep on the couch, and the TV suddenly goes to static while a shadow moves over her, as if the demon's going to consume her, before she wakes up, the shadow disappears and the TV goes back to normal. Especially bad if you tend to fall asleep on your own couch with the TV on.

The Third Movie

So the trailer starts off reasonably, right? It cuts between young Katie and Kristi and stock footage from the first two movies. Then it cuts to them in the bathroom attempting to summon Bloody Mary. It doesn't seem to work, and they leave the bathroom, oblivious to a shadowed figure who looked suspiciously like Possessed!Katie standing right there in the mirror, watching them walk away. The audience only sees a shadowy figure, but it's still pretty creepy.
- While the aforementioned scene never takes place in the movie, the movie does have, if you will, its own version. Randy stays home with Katie while Dennis and Julie take Kristi to the hospital for a fever. Katie wants to play Bloody Mary. Once they turn the lights back on, Randy has a scratch on his stomach. The demon then starts slamming on the other side of the door. By now, Randy and Katie are thoroughly terrified. Slowly, Randy opens the door and the demon throws Kristi's tea party furniture across the room. After this, Randy packs up his belongings, tells Dennis to watch the tape, and that, in a nice way, he is completely fucked.
Following the earthquake scene is the shot of the dust from the ceiling covering the demon. -shudder-
THE SHEET. OH GOD THE SHEET.
Any scene with the oscillating (side-to-side) fan:
- The babysitter jumps in front of it for a "gotcha!" scare.
- Camera pans left. White sheet on top of, presumably, one of the kids. Camera pans right, the babysitter is sitting quiety. Camera pans left, the sheet-wearing kid is gone. Camera pans right, the sheet-wearing kid is standing right behind the babysitter. As the camera begins to pan back to the left, the sheet drops and you realize it wasn't one of the kids.
- Camera pans left, as the mother walks over to the front door in response to someone knocking on it. naturally, being a ghost movie, there's nobody there. She walks back to the right, and slows down in shock as the camera pans back to the right, and we see that everything that isn't bolted down is gone. This includes the table. There's a Beat, and everything comes crashing down, having somehow been suspended above-camera.
Kristi decides that she doesn't want to play with her imaginary friend any more. He is not happy about this. The following night-time scene, we see objects in Katie and Kristi's room coming to life. The demon throws Katie's blanket at the camera, moving the bed around, and forcibly dragging her out of bed into a cubby hole. The demon stops once Kristi decides to play his game again.
The final night. That's all that needs to be said.
- The old ladies. They were billed as "creepy ladies" for a damn good reason.
When Katie bumps into Toby. Toby doesn't like to be touched.
Maybe more of a fridge horror but the demon goes under 9 year old Katie's covers. And disappears inside of her. Say whatever you want about this but it's simply terrifying.
The demon filling the parents' room with white noise so they wouldn't hear their children screaming and crying for them.