What are you looking to spend?  And what kind of gun?

Shotguns are good H.D. and run cheap (about $200ish)

A handgun can run about $600 and is more compact and I don't know if CO has open carry or what their gun rights are.

X

If you're looking for a handgun, I strongly recommend looking at the Springfield XD line.  They generally retail in the $400-$500 range, they often come with multiple magazines (and occasionally a magazine and case), and they're incredibly reliable.  I used a Springfield XD Service (4" barrel) chambered in .40S&W as my primary carry weapon for several years, and it has been my main home defense weapon since I bought it six years ago.

My favorite aspect of the XD is that it's incredibly accurate right out of the box.  It points very naturally for me (as opposed to Glocks) so I didn't really have to "learn" to shoot that particular weapon.

XDs come in a number of chamberings (9mm to .45 ACP), barrel lengths (3" to 5"), and grip sizes (regular XD and the higher capacity XDm model), so the sky is really the limit.  If you're looking primarily for a home defense weapon, I'd recommend going for the "middle of the road" across the board.  The XD .40 Service (4") is small enough to be manageable, powerful enough to stop pretty much anything, and offers a high enough capacity to put down a group of bad guys.




-b0b
(...can provide more information if needed.)

I think a .40 XD would be perfect for your price and what you may need it for.  Just don't forget to get hollow points!

X
(XD Luv0r for Life!)

I would say a shotty and a cheap handgun, two is better than one.  I like to have a gun everywhere in the house, you never know where you will be when someone kicks in your door.