After my NAS suddenly stopped booting, I bought a cheap USB hard drive enclosure, plugged it into the Pi and now my Pi is a poor man's NAS.

Over the last few years with the raspberry pi people selling their inventory to enterprise customers instead of the hobbyists that have using them for 10+(?) Years ive found that x86 thin clients are actually a much better option in terms of price and upgradability. Most modern thin clients (wyse, HP, etc) have m.2 storage expansion, sodimm sockets, and sometimes even pcie expansion. If you get lucky you can get a decent current-ish gen thin client for ~100$ depending on the specs. What are pi 4s going for these days?

pihole is basically it at this point. Got eonugh spare machines sitting around to do the rest anyway

I mostly use my 3B+ as a development and sysadmin sandbox. Lately I've been using it to test out a few IoT-type projects.

I'd love to get my hands on a Pi Zero W at some point, but chip shortage.

One for pihole. One for Home Assistant. One for an office dashboard.