Too many lightweights in here. Jeez. I've been doing this gun thing for a long time. I have many guns and have done more research than 99.9% of your sheople repliers. No, really, they're feeding you mostly BS.

Here is the straight and skinny:

You need 4 guns.

Shotgun - Pump - $200
Large Bore Pistol - 357mag / 9mm / 40 S&W / 45 ACP - $400
Semi Auto Rifle - AK / AR / Mini 14 / M1A / M1 Carbine - $600
22 Rifle - $250

If you drop one, drop the 22 rifle.
If you drop two, drop the 22 rifle and the semi auto rifle.

Get a good pump shotgun, preferably that will hold at least 5 in the tube and one in the chamber. This serves as good castle protection. Use larger bird shot - #2 and #4s. At less than 30ft the shotgun is basically like a super large rifle. The #2s then give you a little more range (out to 50yds).

Get a good quality large bore pistol. I recommend a 357 magnum revolver with a 6" barrel. They shoot fairly accurately and they have a lot of power. YOu can use lower power 38 special loads for lower power applications. If you really want to rock and roll, you can getyourself a 44 magnum. Turning one loose will make whoever is attacking you piss their pants and deaf. Tons of choices here. From lots of rounds to real power (like the 44 mag).

For longer range protection, a good hi-powered, semi-auto rifle will do good things. Works as secondary castle protection, too, with the right ammo.

A 22 rifle will give you the ability to hunt and control pests. With the right ammo, you can shoot, virtually undetected (cb caps) or, with regular rounds you can take down even deer with well placed shots. (Don't argue with me! I've done it!!!)

Just remember: If you can't protect it, you don't own it.