My dad was a commercial and industrial electrician for 30 years before retiring. I'm just so glad this never happened to him.
I've asked him before if he's ever been shocked. He remembers being shocked by a 240 volt line at a wall box once. He was putting the box in, and had both switched off the breaker, disconnected the wire to the wall box he was working on, and left a note. Some bozo hooked the supply back in and reset the breaker when my dad's screwdriver was touching the unexpectedly hot lead into the wall box. He was touching the metal shaft of the screwdriver, and another part of his hand was braced against the grounded wall of the box, so the current never went further than his wrist before exiting his body.
After that scary incident, he always made sure of two things: that the tools he used were well-insulated, and that the breaker he was working on had its door securely shut and locked while he was working on one of its circuits.