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 biggest problems with gRPC are:
Plain HTTP can be type safe. Just publish JSON schema or Typespec files or even use Protobuf.
Am I the only one who is weirded out? Requiring a web server for something and then requiring another server if you want it to actually work on the web?
How expensive do people want to make their deployments?