The crazy in this thread will be fun to read.
I think it all depends on what kind of gun you want. Do you want a shotgun? A rifle? A handgun?
If you're thinking of home defense in case of a revolution, you'll probably want all three.
For personal defense you're probably better off with a handgun. There are plenty to choose from, and many have advantages over others, but the bottom line in ANY gun is, it's not effective if you can't hit what you're aiming at. So yes, take classes (they're probably required anyway), and practice, practice, practice.
Even the cheapest, smallest caliber handgun is going to get the attention of the Bad Guy if you shoot him in the ribs or the gut. Even if you catch his leg, he's going to have to seriously reevaluate his need to work harm on you if you've lodged something deep within him from 20 feet away. And that's just with a .38 Special. You get a larger caliber and you're talking immediate stopping power, whether he's high or not.