One of the Petcos near by me had a fair amount of relatively uncommon fish for about a month at dirt-cheap prices- marbled sand gobies for $4, banded archerfish for $8, ropefish for $12, clown knives for $10, congo tetras for $3, and whatnot. Sadly, they stopped getting the oddballs and have since deteriorated in quality. They still get a few nice TC plants every now and then, though.
There was a nice Petco in Virginia somewhere (forgot the specific location) that had violet gobies, red-bellied piranhas, G. tile (sadly in full fresh), freshwater needlefish, fire eels and other spiny eel species, black pacu, and some other fish; which was pretty surprising, as their fish section was rather small. It's been many a year since I've visited that store, and I don't know if they still sell exotics there.