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.
You’re using a purposely convoluted example from the spec. And I think it shows exactly how TOML is better than JSON for creating config files.
The TOML file is a lot easier to scan than the hopelessly messy json file. The mix of indentation and symbols used in JSON really does not do well in bigger configuration files.