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.
The tooling around it needs to be brought up to snuff. It seems like it hasn’t evolved much in the last 20+ years.
I had a small team make an attempt to use it at work. Our conclusion was that it was too clunky. Email plugins would fool you into thinking it was encrypted when it wasn’t. When it did encrypt, the result wasn’t consistently readable by plugins on the receiving end. The most consistent method was to write a plaintext doc, encrypt it, and attach the encrypted version to the email. Also, key servers are setup by amateurs who maintain them in their spare time, and aren’t very reliable.
One of the more useful things we could do is have developers sign their git commits. GitHub can verify the signature using a similar setup to SSH keys.
It’s also possible to use TLS in a web of trust way, but the tooling around it doesn’t make it easy.