I own four in total, though I am thinking of getting another Pi4 2GB for some RetroPi use.
3x Pi4 2GB
Runs Pi-Hole and general desktop duties.
Runs Home Assistant (previously called Hass.io) think of it as a master control panel for all your home's smart devices.
Runs OpenMediaVault, sharing a 1TB SSD across my home network.
I bought a stacking case from Amazon for them all, which I think looks pretty neat. It can stack four Pis in total (all with fans), so if I do decide to get an additional Pi4, I can just add the 4th layer to it.
1x Pi3B+ 1GB
Runs Victron Venus OS, for monitoring energy usage in my solar shed.
This one just sits neglected in the shed, connected to wifi, hasn't skipped a beat in over two years though.