As Charles has already noted, Nancy Lanza was stockpiling weapons and ammunition in preparation for the end of the world. She thought these guns would make her safer. It didn't work out that way.
Instead, her son Adam used Lanza's guns to shoot her multiple times in the face before heading to a nearby elementary school and murdering 26 people, including 20 small children. He then turned his mother's gun on himself.
To say that this is a common use of personal firearms would be an overstatement. But it is fair to say that personal firearms are much more commonly discharged in murder, suicide, and accident than they are in self-defense. That is a fact. Owning a gun does not make you or your loved ones safer. Indeed, a 2009 epidemiological study at the University of Pennsylvania School of Medicine found that people who possessed a gun were 4.5 times more likely to be shot in an assault than those who did not.
If you are purchasing a gun for target shooting or hunting or just for the damn thrill of holding a tool that can take a human life in a heartbeat, well then perhaps you are getting your money's worth. And if your actual intent is murder or suicide, you can't get much more bang for the buck. But for most people, if you're purchasing a gun for self-defense, it is not only a waste of money, on average it is counterproductive. Your own gun is much more likely to be used to take your life (or that of a loved one) than it is to save it.
My hope is that if more Americans understood the truth about guns, fewer people would choose to own them. And then we'd all be a little bit safer.