Sometimes when writing a screenplay you can get so caught up in telling the story through words and dialogue that you can completely forget to craft the movie with interesting visuals. This occurred to me when I was watching Paranormal Activity a few days ago and realized that the moment of the film that left the most indelible impression on me was the final shot. (If you saw it, you know what I'm talking about.) In fact, I'd be willing to be that if you polled a hundred audience members and asked them to boil the movie down to a single shot, it would be that one.
For an older example of the same thing, you could look at The Blair Witch Project - another horror film with an unforgettable final shot - the POV of Heather's camera as she comes into the basement and sees Mike standing in the corner...
Think about it - how many films have iconic single shots? When you hear the title of a movie, what's the first image that pops into your head?
Raiders of the Lost Ark - Indiana Jones running away from the giant rolling rock.
Psycho - Janet Leigh getting stabbed in the shower.
Star Wars - tons of them, but I'd probably pick the opening shot of the Star Destroyer and the explosion of the Death Star.
The Wizard of Oz - Dorothy and her friends skipping up the Yellow Brick Road to the Emerald City.
E.T. - Elliott and E.T. flying in front of the moon on the bicycle.
Titanic - The boat goes down; Honorable mention - "King of the World!"
Yes, I cherry-picked all the easy classic so as to make my point with much less effort. The point still stands - think visually.