The iPhone case from Magpul, famous for making automatic rifle accessories.
Magpul Field Case iPhone 7PLUS
My iPhone7 is used with smartphone battery case whereas my iPhone 7PLUS is used as it comes, but the size and jet black finish meant it often slipped out of my hand.
I tried using the Magpul, the only one I found interesting in a somewhat oversaturated case market.
It is heavy duty in spite of being a smartphone case a smartphone, and like their accessories Magpul has a good reputation with those familiar with survival gaming and air guns. It has the same ribbing design and rough finish as a Magpul magazine cartridge in the same polymer resin as small firearms. The line-up of different colors is also really good!