I have a zero 5 and it's about as minimal as you can possibly get. Personally I like the design of the phone so I hate to cover it up with a case. Plus I keep mine in my pocket and bolting a bunch of aluminum up to it (as cool as it might look) would keep me from comfortably carrying it.
I'm only using a case because of the reception issues caused by gripping the phone (which I do experience without it).
Details here.
