Pijul
It's a version control system, an alternative to git.
I looked at it while hunting for somewhere to store the experience lake, but it didn't fit.
Still, the tool is interesting in its own right. As a production replacement for git it's a no-go. The adoption and the ecosystem are just too small.
My interest is purely academic, a fresh take on version control. It works with changes (patches) rather than states the way git does, so merging is a simpler operation than it is in git.
I'll have to try it out to see how exactly that plays out in everyday work.