In 2004, Eric Heisserer posted what are, ostensibly, a series of emails from an old friend. (The Dionaea House) Someone they knew way back when had committed a double homicide and suicide, and he was driven by guilt to try to find out what had happened to the guy to drive him to it.
As you read them, they start to imply something supernatural. A haunted house kind of story. The original series of posts ends in September 2004, with an addendum which then links to other blogs and even an instant message transcript.
There's more followup a year after the main body of the story took place.
With it, he creates a well-written spooky story that had some people wondering if it were true, some wondering whether he believed it to be true, a few playing along, and many more just enjoying a good scary story.
He also got himself the beginnings of a screenwriting career. He sold the screenplay (not sure if he sold the rights to the story and had a screenplay deal, or if he completed the screenplay before approaching studios) to Warner. While that project foundered, he has, in the few years following, landed some enviable screenwriting jobs: The Nightmare on Elm Street reboot, Final Destination 5, and The Thing prequel.
It's important to show originality as a screenwriter. Eric's example proves that it doesn't necessarily have to be with a screenplay. Despite the unconventional format of the epistolary story, The Dionaea House still has a beginning, middle, and end. It still starts with a strong hook, then builds slowly with background about the character and hints at the story. It follows conventional horror movie tropes (don't go in the house alone!) but presents them in a fresh and very contemporary way.
His writing career began in the tabletop RPG industry, so writing the story in an episodic way makes sense. Combine that with a strong sense of visual description, and you have a powerful story that you can "see" as a movie while you read it.
I just read that he actually sold a screenplay in 2000 and optioned one in 2002, so his breakout project was not his first rodeo in Hollywood.
Regarding the Dionaea House, he wrote the screenplay and then decided to create the online story and present that rather than try to sell a spec. He had begun creating the various sites that he was using to write the story, and, before the whole thing was online, it got indexed by search engines. (Knowing a little about site optimization for search, he accidentally did some great site design by having disparate sources linking back to each other with text containing similar words. This would increase the apparent validity of the site to crawlers.) He literally woke up one morning and there were millions of hits. It took on a life of its own, as many thousands of people believed it was real (or at least that he was really party to someone else's hoax) and reporters, ministers, and PIs contacted him about it. So, as with all Hollywood success stories, there was a bit of pure luck there - he just has a good enough story for it to catch fire when the match came near.