One 9mm...
I guess it depends on what other guns are in the equation...
I'd probably choose one of these three:
Glock G19 (good all around for CCW and home defense)
Springfield XD9 SC (Better for CCW, equally good for home defense, safer than the Glock because of the grip safety)
Springfield Armory XDm (poor choice for CCW, very good home defense, great range/competition gun, and, again, I like the grip safety)