For me, I'm big on value. $ vs quality. I think we all know that you can spend tons of money on a great product, but for the average consumer, there is no relevance. You can spend $1000 on a set of frames, but are they really worth that price for the quality? Probably not. But what I can comment on are some really good design features of certain brands/lines/frames.
Kio Yamato: Flawless b-Titanium hinge design. Flexible and still maintains tension.
Tag Heuer: Magnetic temple design
Minima: Minimalistic design and concept
Urband: b-Titanium screwless design (others are made of surgical steel)
Kazuo Kawasaki: Well made and durable. Mounting the lenses are technician friendly. They took a complicated process and made it easy.
Spectacle Eyeworks: Faux wood, faux stone work (better than using real wood because it is actually adjustable)
Lego (for Children): TR90 temples with adjustable temple tips and stainless steel fronts.
Adidas: Hybrid Memory Hinge is a very simple design and flexible, although it is a very sporty style
Rayban, Persol and Carrera: strictly for their ability to market their products so well, not the frames themselves
Bellinger's Blac: One of the few companies that can use carbon fiber correctly
Cartier: Mainstream but the quality really is good. They screws line up well, their finish is really good, and their golf plated frames don't fade
Those are just some off the top of my head. I'm sure there are TONS out there that I don't know about but I think most of these bring pretty good value for the money spent.