There are a couple I have in mind. Like many techies, I am a huge fan of RSS for content distribution and XMPP for federated communication.
The really niche one I like is S-expressions as a data format and configuration in place of json, yaml, toml, etc.
I am a big fan of Plaintext formats, although I wish markdown had a few more features like tables.
ISO 216 paper sizes work like this: https://www.printed.com/blog/paper-size-guide/
It’s so fucking neat and intuitive! How is it not used more???
sorry to tell you this bud…