The weapon I would bring would be a M1 Garand and as much ammo as I could carry.
You'll die first. It it's squatches or large alien's you'll need that level of firepower, but for Christ's sake, get a lighter, modern weapon that uses mags like an FAL, AR10, G3 or M1A.
If it's Chinese, smaller aliens or zombies, just get an goddamn AR. You can carry a LOT more ammo.
A pump or semi-auto of your choice, cut down to 16" or so.
The .45 of your choice.
My arsenal, assuming I am limited to guns I own:
Imbel FAL or DPMS M4, 870 Riot Gun, FN45.
If I can have anything off the rack:
High-end AR10 with a 26" barrel and $1,200 Nightforce scope or JP Enterprises JP15 w/20" barrel and ACOG, Benelli M4, FN45.
This post was edited on 10/7 at 12:18 pm