A few years ago on check-in my room's safe was left locked by (a) previous occupant. Maintenance used a special electronic device to unlock the safe.
A week ago I was in a casino hotel, the safe was left locked; maintenance used a hex wrench to loosen a small metal plate (showing the safes manufacturer), and I believe he used a metal rod (about the thickness of a paper clip) to open the safe, by inserting it into a hole. This type of safe is not very safe.