My old D&D group from Hobart is re-forming for one week next year. We've done this two or three times before, and it's been a lot of fun.
Before we meet up to play, and before we make our characters, we are collaboratively building the campaign setting by writing its history, using a game called Microscope.
Microscope is a fascinating game where a group of people sit around a table and build a history. You start from a big idea like "the rise and fall of a draconic empire" and then iteratively fill in the middle bits, jumping backwards and forwards through history as it pleases you.
It seems a little bit like improv, in that there's no chance for collusion or group consideration before making a play, and that you have to take what the other players do as a given.
The rules are very well written, and to my managerial eye read a lot like a well-planned retrospective, or structured discussion.
They are also heavily biased toward synchronous play around a shared table, so we are adapting things to asynchronous, distributed play. We are currently in the very early stages of that.
As it is, I haven't actually played a game all the way through—though I'd love to. My hunch is that it will generate an interesting, lumpy, surprising history with some holes in it, which is exactly the sort of history I'm used to in our own timeline.
Looking forward to playing this almost as much as I am to playing the campaign itself.