My Dad's friend was a farmer-turned-builder. He always wore a flat cap despite many of the tradesman on his jobs saying he should wear a hard hat. One day he randomly decided to wear the hard hat that was on the floor next to him. About an hour later, it was a windy day and an old rusty piece of metal weighing about 2kg snapped from 20ft up, the pointy side landing directly on top of his head. Apart from a dented hard hat and a bit of a shock, he was ok. Any other day it would have been instant death. Ironically a few years later he was killed in a quad bike accident, he wasn't wearing a helmet.