A couple of months ago, I decided to try to learn how to make a World of Warcraft Addons. Here's my first addon: MinimapCoordinates. MinimapCoordinates is a very simple addon that only does one thing: puts your current location in the text above the Minimap.
It's so simple, it actually caused me problems when I first tried to submit it to Curseforge. They rejected it until I could say something about why someone would want to use this Addon. Apparently, "They want to see their location above the minimap" was not good enough. So I called it "minimalistic and light-weight", and that passed.
I made it primarily to learn a bit about Lua, the WoW Addon API, and to how set up the infrastructure around Addons. The code is hosted on Github. There's some neat integration where pushing a Git version tag automatically notifies Curseforge and packages up the Addon for download.
MinimapCoordinates is available for both Battle For Azeroth and WoW Classic.
I'm trying to decide what to tackle next. Ideally, it's more complex than this, but not too crazy.