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’ll give my usual contribution to RSS feed discourse, which is that, news flash! RSS feeds support video!
It drives me crazy when podcasters are like, “thanks for listening to our audio podcasts. We also have a video feed for our YouTube subscribers.” Just let me have the video in PocketCasts please!
I just wrote a YouTube scraper and exported to RSS and into my podcast client. Using YouTube any other way is masochism in comparison.