First thing I thought of too.
I'll try to think of the most intense segments that I can recollect for a more intelligent answer later.

... and of course there's the horrible moment when Dick Van Dyke first tries to speak with a Cockney accent in Mary Poppins.

For me there are several. Halloween when Jamie Lee stabbed Michael Meyers with the croche needle. Then also Friday 13th when Mrs Vorhee got her head chopped off. The first time you see Pinhead in Hellraiser.

Another fave is Scream when the killer chases Drew Barrymore through the lawn and then finally stabs her. I marked out big time in the theatre for that.

My all time scariest movie was Showgirls. Whoever wrote and produced it needs to be castrated.

The Dancing chicken legs on the plate of the main character in "Eraserhead" . Director: David Lynch Starring: Jack Nance, Charlotte Stewart, Allen Joseph. Plus several other "gems" throughout that movie. Horror!

Anything from the "Alien" series.

The first time I saw the Cybermen in "Dr Who" - THAT has to be at least 40 years ago. AND THEY are coming back in this latest incarnation of The Doctor. Now WHERE is my place behind the sofa?

Grazie

Time to see "The Cabinet of Dr. Caligari", lots to pick there.

Sweet - good stuff. Thanks folks, although I fear PeterWright has gone TOO FAR!!!!

How about Fay Wray in the arm shackles before King Kong comes to get her?

I have always found the "King Kong Ding Dong Thong Thing" just to hysterically funny to be scary?

Peter is definately on the money - beats my Aliens! Think about it? How many Yanks now fink that's 'ow we Limeys nawh speak - yeah? Cor Blimey, mate, Apples 'n Pears, me ole Cock sparrah!

. . .see? FAR far more scary than ANYTHING Sigourney has done. She was dealing with maybe 40 aliens? But now the whole World has got 500 million Amerians speaking like Uncle Dickie-Bow-Dyke? Yeah!?!?! See? Now that IS scary . .. oh yes . .

it is very hard to define a "shot' - but images that stand out in my mind as far as "feel" goes - Phantasm has several. Carnival of Souls has many. Many poeple love to use the shower scene in Psycho as a "standard" for horror however that is a scene, not a "shot". The "shot" in that film that stands out to me is the shot when Martin Balsam is stabbed in the head and he sort of slides backwards down the stairs...the actual shot where he is falling down the stars. Also maybe the low, looking up, shot of the house sitting up on the hill. hmmm...along the same lines - not horror really but what I would call an iconic shot - the shot of the single tree in the opening credits of Six Feet Under

It is so hard to figure out a "Shot" from a film that is iconic really - unless it is a promo shot or used on the 1 sheet. That being the case - yeah - original Texas Chainsaw Massacre - the shot of Marilyn Burns hanging on the meat hook. The Exorcist - the foggy street with The Exorcist standing under the street light. Silent Night. Evil Night (A.K.A - Black Christmas) - the shot of Olivia Hussy, dead, with a baggie over her head. (The image encased in a Christmas wreath) (Ok, so it is a drawing of a still). When A Stranger Calls - Carol Kanes eyes.

The scene where the convict jumps out from behind the gravestone in the 1940's Great Expectations. I went to "the pictures" with my little, <30 pupils, one teacher school in 1947.
I still remember the teacher telling us exactly how it was going to happen so he didnt have too many kids with hysterics to deal with. Dont forget at that time probably some of the kids had never been to the movies.

The end scene from Carrie where the hand comes out of the Grave.. So Unexpected back then.. The scene in Jaws where the diver finds the head..The exorcist and the demon voice and her head turns 360 degrees and she floats from the bed..

Any shot where the audience sees something bad about to happen behind the character, and the character doesn't see it.

Think: The Alien rising up behind Harry Dean Stanton as he let's the water fall on his face.

- Or Halloween when whozit gets in the car in the garage and Michael pops up in the back seat.

- Or any number of ghost movies where the character is standing at the sink in front of a mirror and we see "something" flash by in the mirror unnoticed by the character.

For audio, the quote from Sixth Sense "I see dead people..."

Amityville Horror is filled with great scenes... the house windows glowing, flies on the window, etc.

I still love the shot in the end of "The Ring" when the girl climbs out of the TV set! I know there was some good stuff in 28 Days Later too but I can't remember a specific shot.

I agree with Texas Chainsaw Massacre, but more specifically the body run over by the 18-wheeler. My friends and I used to watch that over and over in slow-mo, just to watch the body bounce off the pavement...

Also: I thought the camera-drop in Blair Witch at the very end wss spot-on.

Any dream wherein I receive a letter that has a return address that starts" :IRS."

1. The monster comes to life in the original "Frankenstein." "It's alive! It's alive!"

2. Godzilla demolishes Tokyo in the original "Godzilla: King of the Monsters." Or, if you prefer a more modern rendition, the first appearance of Godzilla coming out of the water in the Japanese "Godzilla 2000."

3. The end of Roman Polanski's "Rosemary's Baby" when Rosemary discovers exactly what she's given birth to.

4. The zombies attack in Romero's "Dawn of the Dead."

5. I'd pick a different scene from "Eraserhead," the scene where the woman who looks like she has the mumps tap dances on screeching creatures in eggshells. I still have nightmares about that one.

6. A different type of horror perhaps, but the "chicken rape scene" and the "singing a**hole scene" from John Waters' "Pink Flamingos" have to be two of the most shocking things ever committed to film.

Brian! You total and utter horror! ! I had obliterated your . .No.5 from my MIND! ! !

Do you know what you've just done? You have just wiped out 5 years of expensive therapy! ! ! AARRrgghhh . .

. .. I'm actually shaking with fear . . .

Grazie

Plan 9 From Outer Space: The scene where the devilish scary disintegrator ray from the space ship is turned on the zombie as it approaches the nice suburban folks who llive next to the graveyard and the zombie turns into...a skeleton! Of course this scene is a triple entendre horror: First, the "zombie" was supposed to be Bela Lugosi's part but he had already died for real, so Ed Wood replaced Bela with his chiropractor, who didn't resemble Bela at all, even from behind a cloak with only his hair showing....you'd have to think he could have gotten the hair right, at least....truly frightening.