When I was in elementary school, my dad kept all of his shotguns and rifles in an unlocked wooden cabinet in the family room. My brother and I were home one winter day with the housekeeper, and, out of boredom, I decided to get out one of the 12 gauges. We had been taught to never point a weapon at anyone, so while pointing it toward the ceiling, I dry fired it. Nothing. Pumped the fore end, then pulled the trigger again. BOOM!!! Blew out several acoustical tiles and part of the roof. As it had been snowing, water began pouring in, so I ran to the kitchen and started pulling out pots and pans. Long story short, both my mom and dad were extremely angry but relieved that it didn't end in tragedy. After he got the roof and ceiling repaired, Dad ran a chain through the trigger guards of all the long guns and locked the cabinet.
Wasn't funny then, but he does enjoy telling others that story now.