For the last 2 years David Schirduan and Marshall Miller have been running the 200 Word RPG Challenge. In their own words: A 200 word limit encourages creativity and demands the very best of your editing and writing abilities.
The premise is that this stretches your mind muscles. Some aspects include only being able to use plain text, so that images and formatting are irrelevant to the exercise.
I entered last year with a very simple piece, and then was absolutely floored with the level of creativity brought on by other participants. It's only gotten better.
Interested in what entries might look like? Many folks are submitting drafts and discussing them up on the Google+ community page. Some of these are quite dark. For example, check out this little dark gem called Quarantine, by Sławomir Wójcik.
My entry this year
I decided to do something that I was planning to play anyways: A world-building exercise while playing 7 Wonders Duel (the 2-player game for 7 Wonders that I've been playing a bunch with the wife and daughter).
Last years they had entries both for standalone games, and also for "accompanying" / expansion type games. This year it's all combined. I fully expect it to do extremely poorly with the judges, because it's not really a standalone game, and expects knowledge of 7 Wonders Duel. But I'm really submitting it for those that may be able to use it, as I plan to.
And you? Have you submitted? Link to your entry below, I WILL read it!