Bethesda's Fallout 4 was first announced last year with an appearance from a dog. It was assumed by a lot of people that this dog's days were numbered, and having a dog in the world of Fallout was just a countdown to tragedy. Not so, said Fallout director Todd Howard at the Fallout E3 Q&A panel this afternoon.
The dog will never die.
You cannot kill the dog. Ever. If you point a gun at the dog and shoot, the bullets will likely go through it. If you throw a large piece of metal scrap at its head, it won't gain a scratch. If you throw it off a cliff it will get back up like nothing happened. Don't waste effort on trying to torture a dog (and why would you, sicko?)
However! While killing the dog is impossible, maiming it is not. You can't maim the dog yourself, but it can become injured if it gets involved in a perilous situation. If that happens, the dog will become incapacitated for a time, which is bad for you, because you'll have less of a defense against enemies and you'll temporarily lose the abilities the dog provides, such as fetching distant objects.
Get your indestructible dog this fall in Fallout 4 for Playstation 4, XBox One and PC.