Wasn't a "gun safe" per se, but I had a digital combo fire safe that I probably picked up at the local Costco a few years ago. Well ... the digital part failed and left me with locked box with a nice pistol inside. I popped an abrasive blade on my circular saw and was amazed at how quickly that safe surrendered ... we're talking under 2 minutes
and it dropped apart like an avocado that you slice in two with a really sharp knife. A little noisy? Yes, but nothing totally out of the ordinary, even in an urban setting. I'd imagine that this approach would work for a large part of the safes out there that are not access limited.