Back when I was a soldier I had a Colt XM177 CAR-15 that I carried as my personal firearm in the cockpit of my Cobra in Vietnam and it was an awesome rifle. It was very reliable and accurate.
After I got out of the Army I resisted the urge to get an AR, preferring to stay with the conventional type rifles, so I got a Ruger Mini-14 that I have been very satisfied with for many years. It's very fun to shoot and has been 100% reliable. I can't remember it have any kind of failure at all.
Recently, I softened my views on things and decided to get an AR-15 type rifle in 5.56mm caliber to augment my firearms collection. However, due the sad state of the economy I was on a very tight budget, but wanted to get as good of a rifle as I could for my money.
After doing my research, I decided to get a Rock River Arms (RRA) 16" mid-length upper and mate it with an Armalite lower I assembled using all RRA internal parts. I topped it off with a RRA scope mount and a CenterPoint 2-7X32 mil-dot scope. All-in I came in at around the $900 mark.
It's been 100% reliable and is extremely accurate. I'm happy with it and would recommend RRA to anyone looking for a good AR-15 on a budget.
Here's a couple of pictures: