[OMFG!You'reActuallySmart!]

Sentry safes are good at protecting from fires and water, but not from someone who wants to open it even if they don't have the key. You can use a screwdriver (flat-head), small coin (dime or penny if you want a challenge), small knife and possibly even a paper clip. Alternatively, you can buy (or make) an actual lock pick set and the safe opens very easily. Most of these would leave a mark on the actual lock around the edges, except for the lock pick and paper clip. I'm sure a few good solid blows from a hammer may do the trick as well, although you may not be able to close it later on.