Bridgeburner
5150
One gun... that would depend on how important carrying is to you I guess. My choice would be a handgun since I carry 24/7. It's not ideal for all situations and is actually particularly lacking in many, but it's my constant companion. I'd probably pick the one that I have right now, the CZ P-07.I would be interested in knowing what gun people would chose if they could only have one gun. I would start a new thread but I am new and can't do it yet I guess.
I would pick a Ruger mini-14 .223 Ranch Rifle. Its one of the most versatile guns out there. Short barrel to make it adequate for home defense and working in tight spaces, but also accurate enough with a scope that you could hunt.... or defend your home at distances. It just does everything. I love my Ruger mini 14.
Now if we're talking about a particular situation where concealing in daily life isn't a consideration like a zombie apocalypse , you gotta go long gun. Probably an AR variant or a Remington 870 for me.