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 appeal for json and yaml is readability, and partially ease of parsing. I say s-expressions win over both in both aspects.
Can you please expand on your references to no-sql and your reference to “lightweight markup”? I don’t quite understand what you meant there.