A close-up of the Just Right Carbine in 9mm with the 33-round Glock magazine inserted. No, the charging handle isn't missing, it can be removed and swapped to either side to suit the user's preference.
What else but the AR-15? Not the M16 or M4, unless you are very disciplined about keeping the selector to Semi instead of giggle. Especially if you are faced with a street full of zombies, you don’t want to go wasting ammo, making noise instead of composted zombies. And you want one lightweight, handy, durable, and with a light on it. No oddball calibers -- sorry, fans of the 6.5 Grendel or .300 Blackout -- but one that will take plentiful .223/5.56.