Loudon Guns in Leesbur has a nice selection, albeit pricey. More genteel than most, with a broad range of sidearms, knives and optics. I've purchased a single action from them.
Purcell Guns in Purcellvile is also a nice/small shop. Smaller selection, but the owner Dale is a good guy. I've a snubbie and deer rifle from him.
If you are interested in Glocks, the Trading Post in Wasington, Virginia (near the mountains) has good prices, but the selection for sidearms is limited.
Nice drive on a motorcycle, however.
Been out to Clarks Brothers a couple of times. Enjoyed the ride. Found shooting range too loud under the tin roof. Surprisingly, the NRA range (indoor) was quieter.
The NRA mueseum (off of 66) is open daily from 10-4 and is free. If you are anything like me, you will be VERY impressed with the breadth and depth of their collection.