Not a lot my M1A Socom wouldn't take care of, accurate, fairly compact, light for a battle rifle, 20 round standard mags, smaller mags available if necessary, and powerful. Has a removable picatinny rail for a scope or you can put a red dot on the main rail farther down the rifle (which I did) or just use the iron sights.
If a handgun makes more sense (which in my current situation does) then my Smith & Wesson 329 PD 44 mag as others have suggested as well. Light, powerful, packable, concealable, accurate.