You know what, after reading all these posts, I changed my mind. I would go with any high power scoped rifle. With that I would start dropping people with .22 guns and take their guns and ammoJ.
Until you get one of them that's a damn good shot to plink you with a mag full =P
Neither of us should even be commenting and or joking about shooting fellow gun owners. Everybody knows in SHTF you need people on your side that you can trust.