When I did tech support for a telecom company, I was assisting on an install. Just as we walked into the data/switch room: the building went dark, the emergency lights came on and the Halon sprayed. I saw a tech from another company yelling over by the open-frame power distribution unit. I looked around for a wooden stick and couldn't find one. By that time he was free from the power distribution unit and seemed to be mostly ok.
He admitted to working on the high voltage section live as he didn't have permission to shut it down during the day. Fortunately, the current did not arc across his heart. It only made a section of his palm, about the diameter of a silver dollar, hard as leather. And, the pair of vice grips he was using was welded to the frame.
Really strengthened my resolve to always be really, really careful around electricity.