I may have told this here before, so forgive me if it's a repeat to anyone. I was newly married in 1978 and the following winter we moved into a larger metropolitan area where I felt I needed a handgun for the house. Being winter (where construction work naturally slows down) and during the worst economic times of my life, I ended up with a Ruger Single Six, and for some reason had it loaded with shot shells.
The wife was cooking supper and I was playing with my unloaded gun (Yeah, right. I only thought it was unloaded), when I pull back the hammer and purposely pointed it at the floor and pulled the trigger.
Boy were we both surprised to hear a gun go off in the house (trailer). Fortunately 22 shot shells didn't penetrate the shag carpet, padding and subfloor. No holes could be found, so I did not have to tell the landlady about it. Even more fortunate, at least one of the rules for handling guns stuck with me. Keep your firearm pointed in a safe direction at all times.
One other time, more recently (another Ruger single action) my cotton gloves slipped off the hammer while I was farting around with my .41 magnum in a deer blind. 10 years later, I still have a hole in my blind, and my ears are still ringing. They ring all the time these days.