Ok I've rethought it... all I need is a 12 gauge with six shells and my 45 with two magazines after all I'm just trying to get to the Twinkie factory in quahog
G19 and AR15 with a couple 30 round mags of 5.56 and a .22 converson unit with 1K rounds. Honestly, these are my first choices because they're easily the single most popular weapons used by civilians. Ability to share parts, mags and ammo is crucial. Now, as to why they're the most popular, it's because they offer some pretty distinct advantages over many other platforms.
CZ Rami 9 with 4 full mags and 500 rds of 9mm and Mossberg m590A1....or the Marlin 60 and all the .22 I can get my hands on.
IF you'd given us the choice of 3 guns, all of those would be mine.
I carry the G26 with IDPA mag set up and the AK 74. 5.45 x 39 ammo is lighter, got 9 mags, 1 in weapon and 8 in 2 mag pouches on belt ready to go with cleaning kit. Wife gets Kel-Tec Sub 2000 with green laser because it folds into a backpack easily and the six 33 round Glock mags loaded with Golden Saber Hollow points also fit the G26. Wife also gets Ruger P85 cause it uses 9 MM too. Poor kid # 1 gets Ithaca model 37 Fearherlight with 50 round bandolier, kicks really bad with Nobel Sport 12 pellet buck and Wolf slugs out if the smooth 18.5 barrel aren't really accurate, might as well give him the P3AT too. Kid # 2 gets Remington Nylon 66 22lr with scope and 1000 rounds. I live in the city and have no illusions about finding ammo or living off the land. If SHTF it'll be a panic followed by looting and violence.