Here is a list of version control systems on Wikipedia. There are a lot more than I realised:
https://en.wikipedia.org/wiki/Comparison_of_version-control_software
Are you using an alternative to Git? What are your reasons for choosing an alternative? What do you like (or dislike) about the alternative you're using? And would you recommend it?
What would be REALLY interesting would be someone taking a snapshot-happy copy-on-write filesystem (btrfs, nilfs2), and putting a version control layer on top.
Sort of like the old clearcase versioning filesystem (used that 20 years ago ...)