IMO, the bigger the better. I personally do not beleive a .22 is effective enough for personal defense, but I'm sure some people would disagree. I would say keep your eye open for a good deal on a 9mm or larger.
The simplest way to answer the question is: "What caliber would you consider too small to stand in front of?"
A well placed shot from a .22 will kill a person just as much as one from a high power rifle. Any port in a storm..........it's better to have something and not need it than need anything and not have it. Most effective, probably not, but if it's all you got, then it's the best thing for the job......until something better replaces it.
Yea, the vast majority of people will agree that a .22 is not an acceptable round for self defense. You need to look at something in the 380/9mm to .45auto range for concealed carry. You can definitly hurt/kill someone with a .22, but it's simply not an effective stopping round. Utilize the search engine on here and you'll find thread after thread answering this same question.
Yeah what the other guys said...the 22 is better than nothing, and can kill with one bullit, but for self defense you need something that will stop the threat before it gets to you...whetether that be a 350lb meth head, armed robber, or just a crazy animal out in the woods, if something is charging you, do you think that little 22 bullit is going to stop them in thier tracks? Only if you are very lucky, and I would definitely not feel safe with it...but its better than nothing, no doubt about that..
The .22 has it's place in the firearms industry, and yes, it can be a lethal round, but I would never carry one, and/or depend on one, as my primary self-defense weapon. But, it's still better than having nothing at all.
About the only reason why firearms manufacturers still insist on manufacturing and selling palm-sized .22 pistols (pocket rockets), is because the public is still buying them.
^I'd have to agree with that but I still love my .22's - all 5 of them!^
A .22 beats nothing and it is lethal but lacks the power to be a fight stopper. I've killed 5 deer with a Ruger 10/22 at up to 75 yards so I know it will work but now that I have the funds I carry nothing less than a .38spl or 9mm with good ammo and a .308 for deer.
It's not often the caliber that persuades the BG to turn and run, but that fact their victim is armed.
Locally, there was a recent home defense where the elderly woman put a single round of 22 rat shot in the guy's belly. He decided robbing her was a really bad idea, turned and ran, and was later arrested at the hospital.