Narrativemagazine.com has all sorts of writing contests. There are entry fees, but the prizes are big. They usually have a weekly puzzle, but the most recent was a contest for best six-word story. I haven't had time for much serious writing effort outside my current class, but six words? I couldn't resist. It turned out to be a great writing exercise. If you can think up six words for a story, those six words can get your muse moving toward 600 or 6000.
My six-word story: I could not tolerate his thinking.
A contest winner? Probably not. A longer story waiting to be written? Yep.
What's your six-word story?