I use a 3B as a low-power NUT server and power orchestrator with my UPS and a managed PDU. It's set up with a read-only file system to protect against corruption. It's connected to the UPS for status so that if power goes down it can manage the power off timing for servers and network gear. I have a low power rack and a long runtime UPS to keep the core Internet access components up as long as possible.

If the UPS runtime ends the 3B gets a bad shutdown. But with the read only fs it'll happily boot when power returns and then it brings up all the gear in a controlled way. This has saved me a couple of times already while traveling.

I want to have a smart frame (calendar and photos, maybe some home controls) with my zero, I’m just too lazy to actually do it. There are also cool “smart mirror”s I’ve seen. Zero can also become a WiFi pwner (https://pwnagotchi.ai/) and gameboy sized emulator

My Pi2 is my Christmas Tree. I think the older version is discontinued, but they have this one:

https://thepihut.com/products/3d-rgb-xmas-tree-for-raspberry-pi

It's super simple to put up and take down. :) I have an sd card with the software set up to automatically run the lights when booted. I keep a bluetooth dongle plugged in, and when a cron job recognizes that the bt dongle has been removed it shuts down the rpi. Simple solution and everyone who sees it loves it.

If you have a 3D printer, ou can make a wifi enabled camera out of the zero 2W if you buy a small raspi cam module and connect it to a powerbank and or solarpanel. As a security camera or if you add some basic motion detection a nature/animal camera.

400: 8-bit computer emulators (i.e., Commodore, ZX Spectrum, Amiga, etc.) since the form factor would be reminiscent of those.

3B: Network camera

Not sure about the Zeroes and the 1A because I'm not entirely familiar with their capabilities.

You can still easily use them to host some stuff on the internet, like a chat bridge or bot etc.

You might be able to make an ADSB reciever. It's transponder signals that power sites like ADSB Exchange

https://www.adsbexchange.com/hardware/

You could still use them as small, tangible containers.