My first project that I started in order to teach myself Elixir, and a project that I still return to so I can experiment with new stuff, is a BitTorrent client. Elixir is phenomenal at it. Managing a ton of connections, parsing binary messages, and allowing all that data to converge into one place. It’s been really fun.
Recently I’ve been trying to make an event store for event-sourced applications with the hope that I could monetize it someday, but I don’t have the attention span to stick with it long enough to get it off the ground lol.