Water pulsing / banging from shower
It sounds like water hammer to me. With just the right flow it can get very loud. There are 2 ways I know of to eliminate this: 


Have a section of pipe at the faucet that goes up and is capped. The trapped air creates a cushion which can solve the problem. 
Or use a commercial water hammer arrester. These do basically the same thing and are smaller but cost more.