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.
I had the fortune of being hired to build up from zero my department, and one of the first “rules” I made was all dates are ISO-8601 and now every process runs with 8601, if you use anything different your code is going to fail eventually when it finds another column date in 8601.