I don't know if you're talking about the gun industry in general or firearms manufacturers in specific, but I've been especically pleased with Springfield Armory, Crossbreed holsters, Missouri Bullets, Mec-Gar magazines and MidwayUSA.
There have been plenty of other companies that I've dealt with and had no problems, but those are the ones I can think of offhand where the transaction required something extra - either to fix a problem, answer questions, applying a special discount to an order, etcetera.