Can't we all just get along?????
There is a reason they call it a SHTF situation, people. Social order will fall apart. You cannot assume that your will be using you firearms to protect yourselves from JUST movie style badguys. You will be defending yourself from all types of desperate people; from the typical poor urban ghetto dwellers that did not have the money to be prepare, to the dad down the block with the 5 kids who did not have the time to prepare, and the uber gun nut who rather spend thousands of dollars on Class III automatics and nothing on emergency food and water. You may have to defend yourself from all three.
Handguns are definitely the way to go, and they need to be high capacity. In the War of the Worlds type of situation, when you run into a horde of desperate people, you definitely need something with a lot of shots and the ability to reload fast. Carrying only one 5 shot revolver is not going to cut it. Also, everyone that can shoot a firearm in the house should be armed. If something bad happened both my wife and I would be packing, as my kids get older and start shooting, they would be packing. I also like the idea of pistol caliber carbines and rifles with foldable stocks. I'm taking a serious look at Kel Tec Sub2000, since I already own a lot of Glocks, and the thing folds to almost nothing. Let say you have a 9mm handgun and a 9mm carbine it just seems so easy to grab both weapons, extra magazines, and a couple boxes of 9mm ammo and get out of dodge, then to have to grab multiple weapons with different ammo.
I do see a need for a longun, and if I was not going to go with a pistol caliber carbine, I would definitely go with a foldable stock shotgun, AK, kel-tec .223 carbines, or maybe a ruger 10/22. Depending upon the situation walking around with a longun exposed may or may not be a good thing. At least you have the option to hide it better if your longgun has a foldable stock.