Ah jeeeesh. There will be a million suggestions, but only a few are worth really taking to heart. Mine is one of them.

If you want an AR15, here are the questions you need to ask yourself:
1. What is the purpose of the rifle?
2. What is the budget.
As far as purpose goes, if you just want a shooter and dont "need" anything special, then simply look for a Colt, Bushmaster, or Rock River Arms. Those three are the tops for the civilian market hands down. There are other brands that are just fine, but nithing sticks out about them and they are are relatively new to the AR15 game (DPMS, Stag, S&W, etc), and the only brand I suggest you stay away from Olymipc. Just look for a basic AR15. My stock Colt AR15 and I used to nail prairie dogs all day long at 200 yards very consistantly (3in or less groups at 200 yards). You dont need a $2000 rifle to be accurate, you need a good trigger and optics. Dont worry about all the BS.
Right now, since Obama and his buddy Holder are made it clear thay *want* to reinstate the assinine "Assault Weapons Ban", the prices have just jumped from %10 to $50 depending on the model of evil rifle you're buying. You can still find a nice and accurate (and stock) AR15 rifle for less than $800 if you watch closely.
I've been around AR15's for the last 20 years and have put thousands of rounds down range at varmints, targets, and steel plates in competitions. I reload my own ammo and put 100 or so rounds down range a month on average (more in summer, less in winter). My own AR15 is a Colt MT7600 that has been put back into "natural" form. Since it was built during the AWB in 1999, it came without a flash hider, no bayonet lug, and it also had a HBAR (heavy barrel). I sent mine in after the ban and had threads put on for the flash hider and the barrel milled down to "government" specs. Now, my rifle is exactly like the M16"A4" that US Marines are carrying (minus the full auto/burst). Mine also has mounted on top an ACOG TA31 w/ "donut" reticle. It is a sweet rig and I am glad I'm the giver and not the receiver. Any baddie out to 300 yards is going to have to be well hidden from me in order to be safe.
Feel free to PM me with any questions.