M1 Carbine, hands down!
With DPX it's excellent in stopping power.
Low flash in the dark.
Low blast inside a house.
Light, short, easy to handle.
Up to 30 round mags.
Kicks not much more than a .22.
Is 'PC' and cheaper to get than alot of other tested battle rifles (CMP is the way to go.)
Sure I have other rifles and shotguns, but the M1 C is my most useful.
"The government has confiscated all of our rights and is selling them back to us in the form of permits."