I have a weakness for tools that are a little hard to explain.
They are usually small, slightly illegible, and easy to make sound less interesting than they are. A bottle. A notebook system. A command line program that looks unfriendly until you realize it lets you think in a different shape. A field guide. A musical instrument. A piece of algorithm a few hundred people love in a way that is hard to summarize.
For a while, I called these “niche tools”. The word was partly true and partly lazy. “Niche” describes the size of an audience without saying much about the quality of the need. A tool can be niche because almost nobody wants it. It can also be niche because the people who want it have not yet learned how to explain what it gives them.
“Strange” feels more useful.