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 hate grammers in anything that don’t support trailing commas. It’s even worse when it’s supported in some contexts and not others. Like lists are OK, but not function parameters.