I voted for the 380 ACP, since my Kel-Tec P3AT is my current "in the neck holster t-shirt and gym shorts gun." In all honesty if I ever get a hand or wrist injury that limits what I can handle I'd be out shooting ping pong balls with a 22lr J Frame or SP-101, or a 32 ACP CZ-83. I must admit that I have this strange desire for a Baby Browning (25 ACP) though, and I'd probably carry it too. All that to say the P3AT is the biggest small gun I can carry when other options just aren't practical. Tailor the gun to the need and carry the largest caliber that you can comfortably handle in that size package. Another example; if I'm ever around small children with frequency, in a low threat environment, a 3" bbl J-Frame "kit gun" in 22lr or 32 S&W may well find a home in my safe since the soft report will be less likely to damage sensitive little ears. Like I said, fit the gun to the parameters of the situation.