Spigen Galaxy S6 Card Holder
Spigen makes a lot of different case options, designs, and of varying thickness. The new Spigen Card Holder for the Galaxy S6 is a wallet case too, but like the CM4, doesn't flip open. Instead they have an insert integrated in the back. It protects the entire device, including the protruding camera lens, and has a safe place for you to store your credit cards.
It has a soft TPU lining inside for protection, and a hard polycarbonate shell on the outside for durability. It's available in 8 different colors and comes at a decent price too.
Buy it on Amazon for $18.99