What could i do with my Raspberry Pi's?

Hello everyone,

i hope this community will get a bit back to life.

I have a lot of Raspberry Pi's at home, laying around and collect dust. Most of them are RPi 4 and one or two are RPi 3.

So what i just made with them:

1. A Litecoin-Miner for a schoolproject:
It's not mining anymore since the power is to less, it would need over 100 years to reach the minimum pool withdraw of 0.1 LTC.
2. A Hidden Service (Website on the TOR-Network, the Darknet):
I use a RPi 4 to run my hidden service. It's a link-list to many sites of the darknet. I tried to find some cool links like social networks, forums, news pages, etc. But i don't maintainance it anymore because of lack of time. So i guess i'm shutting it down in the near future.
3. NAS with Mediaserver:
A (not that) simple NAS using Open Media Vault and Plex for watchung my movies. Why i wrote nit that simple? Because once it was also some sort of "moneyprinting machine": I've thought 'The server is running for 24/7 but i don't use it most of the time. So why shouldn't i put some IP-Sharing services on it, so at least i get a bit of money?' At some point a harddrive went full and i couldn't figure out why. Also the moneyprinting part didn't worked easy, so i set it up again, this time with a RPi 5 instead of the RPi 4, more HDDs with more space and more organized. The "moneyprinting" part i let away this time.

I know most of this is some basic stuff i made out of RPi's. And i have so many of them laying around. What are some other cool projects i could make with them?

Give me some suggestions in the comments, or tell us what you did made out of an RPi!

Sincerely,
BlackButterfly666