When my Dad worked in a power station, one of his colleagues got blasted by 66,000V, directly from a multi-megawatt generator. Severe burns, but he lived. That's quite amazing, given the low impedance of the source.
The scariest situation I've been in is doing measurements on the live busbars at the entry point of a skyscraper. The electrical cabinet contained a wall full of uninsulated high-voltage gear emitting an ominous 100Hz hum, as the bus bars vibrated in the EM fields. All I could think of was "don't fall forwards".
