Most Durable: Otterbox Armor Series for iPhone 4/4S (price TBA)
Otterbox’s newest and toughest case can withstand a 20-foot drop, 30 minutes under 10 feet of water, and two tons of pressure, all without letting in any dust or debris. The Armor Series boasts a thermoplastic shell and a precision fit (within 0.003 of an inch) locked under a medical-grade stainless-steel latch. Its rectangular shape and black color refine the appearance and day-to-day functionality of previous models, though this series remains somewhat cumbersome. The headphone jack, speakers and mic are completely waterproof, as is the entire case. Consider this the Fort Knox of iPhone cases.
Our tester said, "I'm always by my pool, so I decided to test it out. Sure enough, not a drop of water touched the phone when I removed the case. This thing is great for water junkies."