Kettles & Toasters & other things that trip mains RCDs.
Once we'd grown large enough to require something more organised that "floppy-net" we installed a DEC P60 Novel Server.
Locked in the room that served as the warehouse, hardwire into a switchless socket so no chance of accidentally turning it off or unplugging it.
Feeling pretty smug about power we couldn't understand why the server kept shutting down.
Turns out it coincided with tea & toast time. The hardwired "server" power was on the same ring as the kitchen.
New ring installed, UPS purchased.