So I’ll travel with a Mac laptop and type in “Guest” when told. OS X creates empty guest accounts with few privileges on the fly upon log-in, and deletes them upon log-out.
Otherwise in any system just create a dummy account with few privileges and some bogus documents like “Kip Hawley Sucks” (just kidding, that’ll get you seriously harassed, it’s happened). Log in with that.
Both of these center on not having the opening screen where all available accounts are shown.