Fax Machines
I hate fax machines. For one thing, I never know whether I’ve successfully sent something unless I call the recipient and ask, which somewhat defeats the purpose. Their user interfaces (all different of course) always seem to feature dozens of obscure functions and incomprehensible messages.
People are constantly complaining about how hard personal computers are to use, but they’re hand-holding wonders compared to fax machines, which only do one thing.