You're not really going to see BIFL brands while second hand shopping any more often than "disposable" brands. Like you said in the second paragraph, for the most part you just go into the thrift store or yard sale or whatever already knowing what you're looking for and picking stuff out from there (unless something catches your eye and it seems cheap).

As for BIFL brands, the sidebar is a great place to start. I can't recommend couches specifically, but the best kind of furniture to get is the stuff that's hand-made from hardwood. And as for my best find, I mostly look for/collect electronics so there's not much BIFL material there lol, but if it can be vintage and still fulfill a modern use case (like a stereo system, pencil sharpener, electric fan, fluorescent light fixture, etc.) I'll always go for that.