idiot badge
A mark, such as a scar or wound, that could have been prevented if one ridiculously obvious precautionary action had been taken.
I earned my idiot badge today by scalding my tongue with a freshly poured cup of hot coffee.
Bob failed to properly unload his gun before cleaning it. Therefore, that bullet hole in his leg is his idiot badge.
Bob failed to properly unload his gun before cleaning it. Therefore, that bullet hole in his leg is his idiot badge.