There are lots of cool little guns that you can stuff into a pocket, but as "pocket guns" most have a serious drawback... in many cases, they're too slow to get to action and most of them can't be fired from inside your coat pocket. The small handgun that I consider a true and priceless "pocket gun" is one which can be held, ready to fire, inside your coat pocket, and can be operated from within the pocket without having to take even an extra second or two to pull it out!
This type of weapon gives a huge tactical advantage, tipping the scale back in your favor, should an evildoer try to get "the drop" on you.... a "pocket gun", by my own definition, is a gun you can carry in a coat pocket AND FIRE while the gun is IN the coat pocket. This rules out semi-autos, leaving small revolvers (J-frames or others) with internal or shrouded hammers. I have a Kahr PM9 which many would consider to be a pocket gun and it's an awesome little 9mm pistol, but I don't think of it as a "pocket gun" because I can't shoot it from inside a coat pocket - it's just a small, handy, lightweight little gun... not a pocket gun.
Consider the many situations where you may be (walking on a beach, trail off the beaten path, quiet, dark city streets). You see someone walking toward you, seemingly non threatening, but you don't know for sure. Situation doesn't look threatening enough to cause you to change course or direction, so you keep walking forward toward the oncoming person (or people).
As they come close enough to pass you, they stop for a moment and ask you a question, ask for directions, for the time, for a "light", for "help", or for whatever. They may appear relatively non-threatening and then, while they're right there in your "zone", just a foot or two from you, they suddenly produce a weapon or threaten you somehow. Your worst nightmare is beginning. At this point, unless you're exceptionally accomplished and skilled, it's not likely that you could draw and fire a holstered gun carried CCW quickly enough to save your life. And if there's a gun or knife already pointed at you, attempting to draw your own could easily get you shot or knifed before you can even pull your own. If your weapon is in a holster, around the back, under a shirt or coat, or in your pants pocket, the BG has "the drop" on you. He already has the advantage because he knows what he's about to do and you don't have a clue!
BUT, if you have a revolver with internal hammer (642, 640, etc.) in your coat pocket, you could hold it in your hand, pointed forward, ready to fire, long before the approaching stranger even gets close to you. Then, if the passerby should become a threat, you can fire INSTANTLY right through the coat pocket, if necessary. On the other hand, if no threat is presented to you, you haven't revealed your armed status and life goes on about it's regularly scheduled program.
For this reason, I consider my 642 and 640 two of my most important handguns... and I will carry one of these in a coat pocket whenever I think I may be in a situation which could benefit from it, even when I'm packing a G23, G30, or bobtailed Commander IWB at 4 o'clock, which I typically do anyway.
SO, yes, I think the pocket gun (an internal hammer revolver) is very important and even though the capacity isn't so great and the reload speed is slow, and the caliber may not be ideal...
the ability to be able to hold & fire instantly through the coat, without having to produce the weapon, is worth it's weight in GOLD.
