What's the best, but relatively unknown use of Git you've seen?

I haven't seen this, maybe it was done before but at least I haven't seen it widespread but I'd love to: tutorials.

think that each step is either a branch or a commit. whenever you're done, just switch to the next branch. even if you're git-illiterate, you could have a next.sh for pointing to the next step in the tutorial. same logic for check.sh to verify completion. you have built-in diff for changes between steps, you could work in whatever IDE you like, and it may not be limited to just code, too.

The use of git to track timeseries data is pretty neat. I have one private git repo which a machine will periodically update with it's public IP.

Here is a group that tracks public data sources in git: https://github.com/datasets

It's the data layer of https://www.passwordstore.org/.