Use case vignette
This one was inspired by an NPR story, which described a column in a local paper that was just scenes from various coffee-shops. As they described these tiny slice-of-life vignettes, it occurred to me that this could use a very simple but fun little tool.
So Vignette is an almost trivial App, which lets you record nuggets: observations and ideas of people, plots and scenes. I suspect the main case would be for personal use, but it might also do nicely with sharing -- for example, combined with What's New, it makes a nice little feed.
The core structure here doesn't require any new features -- I could implement it in minutes. The primary models would be things like Character, Plot and Scene, with loose hooks to tie them together.
For individual use for story/LARP/whatever writing, the usage is obvious: it is basically a structured and searchable notepad. But it could also be used collaboratively more or less trivially, using standard Querki access control. And it could potentially be spun up as a crowdsourced tool, with folks rating ideas up and down, the ability to mark "I'm using this!", and so on -- an encyclopedia of story ideas. That could be both fun and rather weird.
It would probably need some creative use of names and tagging, and is probably one of the best arguments for a hierarchical namespace that I've come up with to date: you want to be able to tie a bunch of Things together to build a coherent Scene, if you're building something a bit more complex.