LG G4
I was ever so wary of opening this beautiful former flagship device - curved screen, high performance camera, etc., but I needed to polish out a lens. I got up courage after seeing a YT vid - my god it's the easiest to open/fix device I've seen. Not even silly screws or warranty-void stickers on screwheads, just in, unclip motherboard and peripherals, and you're done. First time I was in in 10 minutes, second time mere seconds. It has convinced me to go LG from hereon in, and there's no indestructible OEM software preloaded either - delete what you don't want.