I used to run a hackspace, so quite a lot! But in no particular order these are some of my favourites:
- A tracking airsoft turret that would point at and fire at movement. Was coded in Processing.
- A world clock of digital clocks that synced with NTP and could be set to many regions when working with different timezones.
- A QFH antenna for receiving live satellite images via SSTV from weather satellites
- A core xy assembly with a peristaltic pump that can be placed over a frying pan to make fun designs of pancakes
- A screenshot tool that uploaded to a private site with a short code URL for sharing screenshots without relying on ott SaaS products