Like some other responders, I would recommend you take another look at a .22 cal auto-pistol.
People who are eager to hurl hate at the .22 LR are curiously reluctant to stand up and take ten .22 rounds square in the chest.
In a home defense situation to some extent it depends on whom you're defending against. If there is someone specific who is trying to get in to get at YOU specifically, then perhaps a .12 ga shotgun makes a better choice.
But if you're scaring off the neighborhood meth head on a hot prowl, a few shots from anything would likely remind him that he has urgent business somewhere else.
As the others said above, a .22 LR that you can shoot very well, very accurately, and that you feel comfortable practicing with several times each month, is going to do you much more good than a larger caliber that kicks like a mule, is expensive to practice with, and that you're scared to shoot. A hit with anything beats a miss with a more optimal caliber. And as said above, any little tiny pistol is going to kick pretty good - its a function of physics.
There are all sorts of opinions out there, and some are better informed and more experienced than others. Regardless of which way you lean, recognize that using a firearm well also involves a psychological element that comes from knowing that you are proficient with whatever you select. Select something, then, that you can become very proficient with.
There is nothing wrong with a .22 LR pistol, if thats the pistol that lets you hit what you aim at every time, in light or darkness, whenever you need to.
Here is one to take a look at:
http://www.ruger.com/products/sr22Pistol/index.html
Just another opinion!
Best of luck to you.