I dont know if they make the case for the 5 yet but im using a lifeproof case on my 4s. Very slim, adds a smidge to the overal length, completely waterproof and shock proof. Comes with an adapter so you can still use the headphone feature.
Only complaint i have is in the name, "lifeproof" my life is working in a machine shop.......and my case died within 4 hours of a work day. All in all tho, before i broke my case it worked flawlessly.