if you are in the Zombie Apocalypse there are a few guns that you want to get your hands on.
in the Zombie Apocalypse shotguns will be used for close encounters like cleansing a building or barn.
you want to get the gun to be short as possible yes your accuracy will decrease but that wont matter within 10 yards with buck shot.
I would take the stock off and put just a pistol grip on the gun and i would also saw the barrel down to a comfortable place.
Most shotgun would work in for this Remington 870s are most common but if you got a hold of a good semi-auto Benelli or Beretta or even a M4 tactical 12 GA pump action.
Assault Rifles are your best bet in the Zombie Apocalypse they are light, fast and very accurate from a long distance. Assault Rifles would be my primary gun because they can do it all in most situations.
M 16, AR 15 or M4 all 5.56/.223 rounds
the Rifle i would use would be a Daniel Defense M4 V7 5.56, Smith & Wesson M&P 15 or any DPMS AR
The attachments for these guns for me would be a front grip, red dot or iron sights and a adjustable stock.
Ak 47 are great guns that are very reliable but it is very hard to find attachments and its effective range is about 400 yards when a M4 V7 is about 600 yards.
AR's can be ambidextrous, easy maintenance, very comfortable to shoot
Any 1911 enough said, A judge would also be a good gun because you can hold 410 rounds in them but would still take a 1911 model any day of the week.
there is no doubt that a 22. rifle would be very effective for zombies they are light and the ammunition comes in bulk and are worth pennies. the bullet was designed to go through the human skull how much more can be said. if you get a ruger 10/22 with a good heavier barrel that gun will be very effective. you want to be very careful with your bullets and keep them in blocks or clips. they don't make much noise when being shot which wont add any unwanted Zombies.