For military (Active Duty and retirees): The Post Exchange (PX) on Fort Campbell, Kentucky has a gun shop, as of mid January. They have a decent selection of handguns, some rifles and shotguns. They never really know what weapons they'll be getting in ... On occassion you can get lucky.
Problem is that the PX is on the Kentucky side of the state line, and they only sell handguns to ACtive Duty military, with orders assigning them to Fort Campbell, or retirees with Kentucky residency. We Tennessee retirees are out of luck. Rifles are no problem, however.
Early February I went in and asked about buying an M4 carbine (I had seen them in before and they always got snapped up immediately). The guy at the counter said that they were expecting a DPMS in, and that he'd hold it for me (I had to leave town for a few days).
When I went to the PX to buy it, it wasn't the M4 carbine, but the longer M16A2 style rifle. I still liked it, but said that I'd really hoped for a collapsible-stock carbine. He went into the back and brought out a beautiful Sig Sauer 556. Pricey, but really nice. I called my wife and asked her if I could get both ... and she said YES!
Paid $760 for the DPMS, and $1560 for Sig 556 ... Saved a bunch of money on the taxes.
A couple weeks later I saw a DPMS M4-style carbine on the rack ... $750. Again, I called 'the boss' and she was cool about me getting it! Again, saved a bunch of $$ on tax.
If you're military (or retired military) and in the Clarksville, TN area, check out the Fort Campbell PX ... No guarantees, as assault rifles are snapped up quickly, but you might get lucky.