Another vote for FRP wall panels...

These plastic panels are installed via FRP adhesive and require no painting or finishing work once they are installed. They are completely waterproof and very durable. You caulk the seems in between each sheet to form a completely waterproof barrier between the sheets and the drywall (or in my case - OSB) beneath the FRP. They are the easiest to maintain since you can simply spray them off with a hose, or wipe them down with an all purpose cleaner... you can also wash a car in your garage with a hose without worrying about ruining drywall. It is a bit pricey - but you'll never have to replace it or repair it.