Glock 19
This is my favorite gun. It is my go to gun. This is because the trigger is buttery smooth and reasonably light/short. It is a 5 lb trigger. The trigger is very important to accuracy. If the trigger is too heavy and jerky, then you'll tend to jerk the gun to compensate and miss your target. With practice, one may overcome a heavy, long, trigger, but if you're a novice and this is your first CCW, then you can't miss with a Glock 19 (pardon the pun). When I convinced my anti-gun wife to go shooting, her very first time out, she shot one big ragged hole with only ONE flier out of a box of 50 bullets using a Glock 19. I was very impressed and kinda suspect she has used a gun before, but just didn't tell me
The only disadvantage of a Glock 19 for concealed carry is that, IMO, it is the biggest size gun you can conceal. It is hard to conceal due to its size. I use a SmartCarry to conceal this. Others may use other inside the waistband holsters such as Crossbreed Supertuck or an over the waistband holster with a large untucked shirt covering it.
This is a 9mm gun and it is the caliber that the US Army uses in their handguns, so it's good enough for me.
Glock 26
This is my wife's favorite gun. It fits in her purse. It is very concealable. It shoots 95% as well as a Glock 19. The only difference between the Glock 19 and Glock 26 is that the Glock 26 is slightly smaller so that it is a little bit harder to aim accurately when shooting further than 20 ft. This is because the distance between the front and rear sights is smaller than on a Glock 19. However, over 90% of self defense shootings are in less than 20 ft, so it really doesn't matter. There are some trade-offs you have to make for conceal-ability. It is a very small and concealable gun. It conceals perfectly in a cargo pant pocket or a purse. It will not fit in normal pants pockets.
Ruger LCP
This is a very small gun and uses a slightly less powerful bullet than the Glock, the .380. Don't let the small size fool you. The recoil is extreme because of the gun's light weight. The Glock has very little recoil because it is like an anvil with a bullet in it. The Ruger LCP is like a credit card firing explosive charged bullets in it. The thing just wants to jump and twist out of your hand as you're firing it. The trigger is 8lbs so it is heavier and longer than the Glock trigger. If you are a beginner, I recommend against this gun as your first gun as it is very difficult to shoot. If you do buy one, also buy a Crimson Trace Laser and snap caps for it so you can practice dry firing it to get used to the trigger. The laser lets you visibly see yourself jerking your gun to compensate for the heavier, longer trigger. It is a great training aid. An hour or so of dry firing with the laser before shooting a box of ammo with it should get you hitting the bullseye every time. A pocket holster like the Desantis Nemesis should work well with the gun.
Kel-Tec P3AT
This gun is just like the Ruger LCP except that the trigger is lighter at 5lbs so it has a nicer trigger. However, the magazine catch release sticks out and if you bump the catch release against something, then it will become a one bullet gun when you use it. It is a little thinner and lighter than the Ruger LCP. You may want to get a very thick holster for this gun so that when you bump something while carrying it, you're bumping the holster, not the mag catch release. To take advantage of the light weight fully, you may want to skip the laser. Just be aware that the puny sights make this a contact close weapon to the novice without a laser grip. It is almost the same gun as the Ruger LCP, so just buy whichever gun is less expensive. A pocket holster like a Desantis Nemesis should be affordable and will work well with the gun.
Smith & Wesson J Frame (438, 638, etc)
There are many variations of this gun; hammer-less, with a hammer, with a shrouded hammer, etc. I suggest that you get one with a shrouded hammer so you can shoot it single action style without the hammer snagging on your clothes when you draw the weapon. The trigger and hammer are 18 lbs. Get an 18 lbs dumbell and try lifting it 1 inch with just your trigger finger. That's what the trigger feels like. The trigger when shooting double action style is extremely heavy. My finger is fatigued and can no longer shoot after only 20 to 30 shots. The hammer is extremely heavy too, so shooting single action style made my thumb bleed. It is a great "get off me" gun because if you push back on the slide during a struggle for your gun, an auto pistol will jam and not fire. A revolver will fire in this situation because there is no slide. Be sure to get the Crimson Trace laser grip for this gun so you can practice dry firing it with snap caps to train yourself to shoot accurately with the heavy, long double action trigger. You can get a leather pocket holster for this or a hip holster. Post on this forum for a used holster and ye shall receive. Used accessories and guns are easy to find for a tight budget because they've been manufactured for so many decades. This is not a good beginner's gun unless you get a laser for it and practice dry firing it to get used to the long, heavy double action trigger. If you're on a tight budget, skip the crimson trace laser. You can duct tape a cheap $5 laser pointer to it and practice aiming with the sights and dry firing it without shaking the laser dot. You can skip the snap caps and just use the empty shells for dry firing, too, if you're on a tight budget. Older guns are cheaper and better. Older guns are made from high carbon steel and will last for many generations if you'll protect it from rust. Modern guns are made from softer metal alloys instead of high carbon steel. I got a new one for $360 so used ones should cost about $310 or less. If you can find a used one that is made of blued high carbon steel, then you've hit the jackpot. Other manufacturers also made fine snub nosed revolvers similar to the S&W J Frame such as the Colt Detective Special. This gun uses .38 special ammo and it was good enough for law enforcement use for almost a century, so it's good enough for me.
Springfield XD & XDM
I have never fired one before so others on the forum should post a review of these guns. I know from the specs on their website that it is a heavier and bigger gun than the Glocks. It also has a 7.7 lb trigger and a grip safety. I did not buy one because of the added mechanical complexity of the grip safety, heavier trigger, and heavier weight. However, on the positive side, it has an accessory rail on the subcompact model where the Glock 26 has no accessory rail but I wished that it did have one.
1911
I have never fired one before so others on the forum should post a review of these guns. They are generally more expensive due to their all metal design. No cheap plastic here. I have heard that the single action trigger is dreamy light and crisp, but I can't say for sure because I have never shot one. I just don't like the added safety that you have to fumble with in a high stress situation so I do not own one. They do look a lot nicer than the Glocks because you could get special grips with them and special engravings, too. Glocks are just plastic hunks of Tennifer coated metal. They have zero style. My wife wants a Centennial edition gold engraved 1911 hand carved wood grips or real Mastodon ivory scrimshaw grips for an every day carry gun. That gun would cost over $2000.00, so I'm going to have to save money for many months to get her one, probably for Christmas. These guns generally use .45 acp ammo. This is the most powerful manstopper ammo against unarmored personnel you can shoot with a auto pistol in a commonly available caliber. There are more power autos that shoot more formidable bullets but these bullets cannot be purchased at your local sporting goods store nor Wally World. For example, I have never seen .50 Cal desert eagle at Wally World.
There are many other guns than what's on this list, but these are the guns that are most reviewed and searched for on other websites. I assume since they are most searched for and reviewed that they are also the most popular guns. However, according to Time magazine in an issue from the 1980's, the most common gun out there is the revolver simply because they've been manufactured for almost a century so there's lots of them out there. Most people who own revolvers buy one and shove it into the back of a nightstand or desk drawer forever. They don't practice with them or use them much so they're in pristine condition as long as they're kept in a dry environment such as Arizona, New Mexico, etc. There's lots of them out there so if you're on a budget, get a revolver because you can get a used one from a friend or family member cheap. I have a friend who gave his revolvers away to my parents when he moved overseas because he thought that they were too cheap so that they're not worth his time to sell.
But as with any gun forum, someone is gonna disagree with ya 
