I'll start with mine. yes part of this was to brag about my somewhat but not too unusual setup. But I also wanna learn from your setups!
Anyways: I primarily use Gentoo Linux.
I have two headless servers: a Raspberry Pi 4B and a Oracle cloud VM (free tier). Both running OpenRC, and both were running mainline kernel with custom config (I recently switched the Pi to PiFoundation kernel due to some issues). The raspberry pi boots from SSD and has no sd card inserted.
Both servers were running musl libc instead of glibc for a while. This gave me a couple of random issues, but eventually I got tired and switched back to glibc.
I have a desktop running gentoo and a laptop running arch, but hoping to switch the laptop to gentoo soon.
Both are daily driving wayland (the desktop had nvidia card and used for gaming). The desktop is running a kernel with a minimal config that compiles in 2-3 minutes.
What's your unusual setup like?
Not THAT unusual, but... I have a Dell R520 server that was leftover/retired from work. I mostly use it for storage due to the amount of disk trays it has. I have all of these disks in a ZFS pool, leaving no actual drives for the OS. However, this was an old VM server, so it has an internal USB 2 port and a ridiculous amount of RAM, so the OS is booted from USB, and I don't use swap.
Boot performance is abysmal (on the rare occasion where I actually need to reboot), but once booted I notice no real downside to having the OS itself on really slow storage. Sure, it's somewhat slow to do os-related stuff such as apt-get, but it's not like I'm in a hurry when doing it. Plus other than updating stuff, the OS storage doesn't see a whole lot of changes/writes.
Now I just need to figure out how to economically attach these 40 additional SAS drives I have. It doesn't have to look good (i.e. fit in the same chassis. Or any chassis at all, for that matter), it just have to work. These additional drives are only 4TB each, but they were free.