There are too many to count, but I can tell you what to AVOID:
Big Bear Arms in Carrolton, Texas. Their resident gunsmith is a nimrod named Richard that has broken several people's pistols (incuding one of mine). Thank goodness the damage was nothing a trip to BCP couldn't fix. Total a-holes.
On to the good...
The Bullet Trap in Plano is good, but their prices are kind of flukey. They are average on some things, kinda high on others and lately have had some killer deals on Colts (like an XSE Commander and a Series 70 GM for ~$550). Nice selection, nice atmosphere, minimal hassles and an indoor range with tons of guns to rent.
I'm sure there are lots of other good places, the phone book is full of 'em. Dallas is a pretty gun-friendly place.