Recently, a friend dropped off her Ruger 10-22 rifle to me because the sling stud was loose. I know it is an easy fix so I told her to just leave it on my work bench and she can pick it up when we meet again in a few days.
I grabbed a cup of hot chocolate and was ready to work. I cleared the rifle and out came a live round!!!!! I was not impressed.
A phone call to her explaining the importance of firearms safety followed. She was receptive and apologized profusely.
Lesson for the day: Check the chamber, always. Firearm safety is in your hand.