If you are looking for the ultimate protection for your iPhone 4, Otterbox Defender case is probably your best bet. Anyone who's unfamiliar with Otterbox products just needs to know one thing, Otterbox cases are TOUGH! See some of the previous reviews here and here.
Back to the iPhone 4 Defender case, this $49 proposition from Otterbox will definitely protect your beloved Apple gadgetry. Inside the box, you'll find 4 pieces of hardware (yes, four!) for protection. The very inner components are two-piece hard cases with felt lining and LCD screen protection that snuggly holds your iPhone in place. You'll then top off the hardcase with a rubber casing that holds everything together. At this point, you pretty much have the actual case/protection ready. Otterbox tossed in an extra belt clip hardware to allow you to snap (or dock) your iPhone into place.
Suiting up your iPhone 4 into the Defender case will remind you of the movie scene where Robert Downey Jr. suits up into Iron Man Mark-III for the first time. You've got a very precise assembly along with a cool see through window which reveals the Apple Logo. All the cut outs are precise and there are rubber flaps protect just about every ports there is to the phone. There will be no doubt in your mind that your iPhone is going to be pretty safe nested inside the Defender.
Otterbox cases are known for its toughness but not for its compact size and this Defender case for iPhone 4 is no different. Its got heft and some weight to it. It kinda reminds me of the Panasonic Toughbooks whereby if you see it, you'll respect it for its toughness. If you are interested in solid protection but wants to keep the bulk to a minimum, Otterbox does carry a couple of their smaller cases such as the Commuter and Impact Series.