I've always wanted my own VW diagnostic tool suite, and between tooling that was released in public on GitHub (https://github.com/kartoffelpflanze/ODIS-project-explorer) and my own research from years ago, it always seemed straightforward but too tedious to execute on. Claude did a great job making something useful, https://github.com/bri3d/mcd-diag-rs , and now I don't have to find a Windows machine or remember a specific diagnostic cable to replace my brake pads.

I also build a ton of household glue stuff; I was never really passionate enough about the whole "homeserver" thing to spend the effort in going beyond basic video recording for my security system, but now I have all of my local-only home automation stuff wired together, mostly into HomeKit, and have been able to ditch a ton of cloud services.