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.
YAML is racist to Norwegians.
If you have something like
country: NO
(NO = Norway), YAML will turn that intocountry: False
. Why? Implicit casting. There are a bunch of truthy strings that’ll be cast automagically.