Yep, you guessed it 10mm for carry! Glock G29.
If I'm in another country, I don't take the 10mm because its hard enough to take a gun on a plane, and import it into a different country! This being said I have to travel with it unloaded, because most airlines won't let it be loaded or its alot more hassle if they do (from my experience), and certain countries don't let ammo be imported or have taxes on ammo, etc, even if its for your own personal use. Also, the better ammo like doubletap, buffalo bore, proload (which I would only consider worth while for 10mm despite a few straggling winchesters, etc), are all special order and cannot easily be found on any shelves in the US let alone abroad. Which brings me to my point, what good is 10mm gun without any ammo? When abroad I usually take/carry Glock G19 or Beretta 92f as ammo is more readily available, the gun(s) performs well with even the worst ammo, and from what I have found, 9mm all around is grouped in a "good" level of accuracy, relaibility, etc. Also those two guns are fairly simple in design and parts are also easily acquired should anything go wrong. I have shot 3rd world .45 where one box was excellent, and the next box wasn't worth loading, but all around 9mm has all been at least worth shooting. I can't say every 3rd world 9mm round was great as some boxes differed from round to round within the box, but overall it has been better than all the other calibers I have shot. I personally consider any cartridge capable for self defense, though I think the 9mm falls at the bottom of my acceptable scale, it is just convienence abroad where it wins out.
PS - The 10mm is my ccw, but it still is my secondary...just gets me to my longgun!