Whoo boy. I would get...
H&K 416 -- Best caliber would be a widely available one, since I'm going to be most likely scavenging or stealing ammo from others in a SHTF scenario. This rifle is basically an upped-version of the M4, though it uses a slightly different gas/piston system that is more similar to the german G36. Some specs: 700-900 rounds per minute, it fires standard NATO small ball (5.56x45mm), but will also fire the civilian .223 Rem. I'd probably pop an Eotech on it since it's gonna be my close-and-busy tool. I'd probably put a 14-inch barrel on her and call it good.
M240 "The Gun" -- This is not exactly the newest of firearms, but it's a beauty. She's big, she's bad, and she's versatile. Can be mounted on a vehicle or used by footsies as a squad automatic weapon. I'd most likely mount it on the toughest vehicle I could find and use it as a mobile weapons platform. I might even coax it with a .50 cal M2. Some specs: 650+ rounds per minute, fires standard NATO big ball (7.62x51mm). I'd mostly be using this weapon as a "crowd pleaser" to keep multitudes of zombies away.
Moss. 500 shorty tactical -- Everyone needs a shotgun. I'd have 12-gauge, a shorty with an aggressive muzzle and accessories like maybe a tiny red-dot or Eotech and a pistol grip. I probably wouldn't need a stock, as this would be my last-ditch, get-the-****-out-of-my-face-zombies! weapon, and I'd need to conserve space as much as possible.
Daewoo DP-51 -- Now, I've been teased about this before, but as a pistol, I'd choose this Korean military beauty. She's smaller than your average American LE/MIL pistol, but really... I've had a great deal of experience with it and of all the pistols I've fired, I could handle this one the best. I used to own one, but due to SCHOOL (arrrrrgh) costs, I had to get rid of her.
I'd have one in 9mm. She'll hold 13 rounds of undead-poppin' fun, and it's a very controllable, easily used sidearm. Nuff' said.
That's all I have time for right now, but later I'll come back and add various weapons as I think of more.
