I have never done this with a firearm. This is why it is important to ALWAYS follow the 4 weapons safety rules.
Probably disclosing a little more than I care to here... but when I was in high school I had some friends over (2 girls and one guy) and one of the girls wanted to see my airpistol. She asked if she could shoot it and I said it wasn't loaded but I could put some air in it for her and she could shoot the air. I put in a CO2 cartridge and gassed it up and gave it to her (If you are following my story you will notice that I didn't check to see if it truly was unloaded). She shot a few times at my floor and then handed it to me telling me she had had enough. Being that I had recently returned from a paintball tournament I decided to muffle the sound while I shot the rest of the air out and put the gun away. I wrapped my shirt over the barrel and put my hand right at the end and pulled the trigger... Numbing pain shot up my arm as the BB went DEEP into my hand. I looked up and the guy was looking at me with his mouth open. "I saw the BBs parting the carpet," he said, "but it all happened so fast I couldn't stop you." I got the BB taken out of my hand and have a nice scar on the back of my hand (because it went so deep that they had to cut it out the back). Needles to say I learned my lesson and ALWAYS CHECK AND DOUBLE CHECK to make sure the gun is unloaded, and then I TRIPPLE CHECK.