The first time my mom fired a gun it was a shotgun...my dad's 10gauge. Even though she'd been told MANY times to hold it tight against her shoulder just before she fired she pushed it out about two inches off her shoulder. The impact knocked her flat on her back where she promptly discharged the second barrel into the roof of the shooting hut.
My dad says it would have scared everyone in the place silly if they hadn't all been laughing so hard. She was horribly bruised over her whole chest, shoulder, arm, and even onto her back.
I was sitting here with my hand over my eye as I knew exactly what was going to happen, blood and all. I made the mistake of firing a Weatherby 300 Magnum on the 300 yard range once and holing it like I do semi-auto military weapons. I don't actually grip the front stock but just rest it in my hand for better accuracy. I hit the bullseye but I also clipped my forehead with the scope. I never shoot scoped weapons so I never even thought about it until the blood was running down my face.