This weekend I'm making 2x RGB to HDMI boards for the Amiga 500 and 2000 computers.
https://github.com/c0pperdragon/Amiga-Digital-VideoIt uses a raspberry Pi Zero as part of it.
Previously I've made a Pi1541 disk drive emulator, a Pi 2 in a Commodore 64 case (using a Keyrah V2 keyboard interface), Octoprint setup to monitor and control my 3D printer remotely, 3x Pi Zeroes in my Spectrum NEXT computers, a stand alone Amibian system (commodore Amiga emulator) in a nice 3D printed case that looks like an Amiga 3000 (using PI 3b+), the usual retropi setups, a pi zero in an empty ZX spectrum case emulating a zx spectrum.
ummm...a couple of other things I can't think of right now.
ETA: Oh I made a pi robot a long time ago that would patrol the house and I could log on from work and watch it monitoring my (now dead) cat.