Most pistols are specifically designed to be defensive tools, and have a certain manual-of-arms that go with their particular operating system. With a quality holster that covers the trigger guard, and an operator's hands that know to keep their booger-hooker off of the bang-switch unless they are meaning to shoot, then any modern autopistol is safe to carry chambered.
Glocks, Kahrs, wife's Keltec (all DAO with no external/manual safety) are always carried chambered. Long, deliberate trigger pull prevents discharge unless it is forced.
Sigs, 3rd Generation S&W auto, Beretta, etc (DA/SA some with safety, some w/out) carried hammer down on a loaded chamber. Safety on- if preferred, but I don't. 12lbs of trigger pull x 3/4" of pull means the gun doesn't go off until I tell it to.
1911/Browning Hi-Power, etc.. (SA auto w/manual safety) carried hammer cocked, safety engaged on a chambered round. So long as you don't screw around with it, and know how to operate your gun, this can be one of the safest methods (especially for OCers concerned about a gun-grab potential) to carry. Most "thugs" will fumble with a cocked-and-locked auto for at least a few seconds, should one be able to get it from you. This time can be used to access and employ a back-up weapon.
-G20