i honestly think that the only time a shot gun should be uses is while with a group when trying to clear a building, a double barreled pump action shot gun is best for this since it can take 2 diffrent types of ammo with out having to reload.
see Remington 1740
Heres the thing boys and girls. The Zombie Survival Guy is a work of fiction written by a man with a good imagination who watched way too many zombie flicks. A lot of the ideas he talks about in the book is basic survival 101, which is what makes you think the book is a great referrence point.
Ok back to the subject of this discussion. Shotguns are going to make a great secondary weapon. I would not rely on one as my primary firearm. I think people have the conception that their going to be good, because of the damage they inflict, and the relative easy of firing one. You don't even have to be dead on target to get head shots. However there are some rather horrible draw backs with a shotgun. First stay away from break down shotguns, even if their double barrels. 1-2 shots then your reloading the damn gun. Second make sure you pick a good reliable shotgun. Sorry Benelli fans Ive had too many bad experience with them you classify the Supernovas as anything more than a piece of shit. Go with a pump, and heres why. Semi autos are nice, but they dont hold anymore rounds, and there are more parts to break down on you. You can get extended feed tubes, so you can hold upto 6+1 in the pipe. Stay with a shorter barrelled option cause lets face it your not going to get much more distance with a longer barrel, and there terrible in close quarters. Make sure you have the right accessories with your shotgun. Shell carriers, proper sling, and even a gas tube style stock would be nice. Takes a little of the piss and vinegar out of firing a shotgun. Pick the right ammo too. With any type of target you really don't need anything bigger than 2 3/4" shells, choose whatver load you want.
maybe Ford will come out with firearms :P