I hate these what if you could only have "1" questions. Makes me crazy. I love the 1911's and have my favorites, I love the 45 ACP as my favorite defense cartridge. But as far as ONE GUN, it would have to be powerful enough for defense, large enough to shoot comfortably, be able to serve as a service type pistol for open carry, and small enough for concealed carry in all weather, and have a magazine capacity to handle ALL situations. If it comes down to your ONE DAMN GUN QUESTION, I'd say the Glock 19 or Glock 30. No wait..... Maybe a Colt Commander or Kimber CDP 4", or a, aw hell........: