Yes. My current one in fact. As it's still a work in progress, I'd rather not divulge what that scene is. (It would be sort of like revealing the last scene of THE SIXTH SENSE before an agent every saw it... not that I'm comparing myself to early M. Night.)

Well, yes. My 'ideas' come in the form of scenes, usually. So, I build a plot and characters around that.

I've often written features based off a single line.

My latest project, "AETHER," started from:

"Some believe it's good. Others believe it's evil. Me? I don't give a damn. All I know is it killed my partner...and that's a damn shame."

Sometimes titles come to mind first and I write a story around that. You might also say that writing a story around a single scene or specific set piece doesn't mean that scene has to stay in the movie. Often those are our favorite scenes, and we end up killing them because they just don't work. But it's still a means to an end.

Like Rod Serling said, story ideas come from everywhere, but it takes courage and hard work to put them down on paper.

IIRC, the Coen brothers' inspiration for Miller's Crossing was the image one of them had of a hat being tossed over a creek. Just that image. As Garrett said, story ideas come from anywhere.

Actually removing an interesting scene from one of my screenplays to create another is something I never considered. My first screenplay was crap, but it had two scenes that would be memorable and could be the inspiration for a nice concept. I'll have to add it to my list.

Yes. All of them. My stories are always a result of a single scene that takes shape in my mind and then refuses to leave until I've written it down.

I don't know where these scenes come from. Probably a mix of lots of things violently shaken and stirred by my brain.

This scene is often somewhere in the middle of the story. I need to figure out what happens before and after. But this scene often carries the theme of the story, a key scene of some sort.

Everything I've written originated from one scene in mind.
I can't imagine writing any other way.