When you leave the house, do you grab your iPhone even before you search for your keys? Once you have an iPhone, it goes everywhere with you. The kind of case you choose for your iPhone says a lot about where you're going.We've picked six types of on-the-go people and the iPhone cases that best fit them. Whether you're an outdoor enthusiast, traveling executive or soldier of fortune, there's an iPhone case that should be just the right fit.[ Learn six hidden iPhone shortcuts, reports CIO.com. | Check out five great iPhone and Mac accessories. ]Adventurer: Otterbox DefenderHard-core adventure travelers never know where they're going to end up. Chances are it won't be at the Waldorf-Astoria. For these folks, only one iPhone case will do: the Otterbox Defender. It's been called the soldier's iPhone case and is arguable the toughest case on the market.Your iPhone will be completely housed in three layers of protection (hard plastic base layer, soft silicon outer layer, plastic holster). Thin plastic covers the screen. Cloth protects the speakers.Otterbox's Defender wards off damage from drops, scratches and dust. The rugged case clips into the plastic holster, which attaches vertically to the belt. All iPhone controls are accessible.However, Otterbox is quick to point out that the case doesn't protect against water\u2014public enemy number one for the iPhone. Fitting the case on the iPhone isn't easy, nor is the Otterbox Defender cheap: $50.Otterbox DefenderGolfer: Mophie Juice Pack AirFor most golfers, the game borders on obsession. They'll spend hundreds on equipment, lessons and green fees. Now the iPhone has become an indispensible tool out on the course\u2014along with iPhone golf apps like Golfshot GPS, which triples as a rangefinder, scorecard and game analysis system.Customer reviews of Golfshot, however, lament the app's drain on the much-maligned iPhone battery. Some app users complain that the iPhone battery dies on the back nine. Others, like myself, worry about the battery getting too low to the point that this becomes a disruptive part of their swing thought.That's why iPhone-toting golfers often spend $80 for the Mophie Juice Pack Air, a relatively sleek protective case that doubles the iPhone's battery life. Getting through a round isn't a problem anymore. Mophie Juice Pack Air comes in an array of colors, including red for shooting under par.Outdoorsman: Pelican i1015Pelican i1015If water gets into your iPhone, well, you can kiss it good bye. Water might even void the warranty. Yet many iPhone apps help outdoor enthusiasts. Divers write entries in the Dive Log app. Fisherman depend on FishHead. And kayakers check water flows with RiverGuide.Keep evil water away from your iPhone with a Pelican i1015 hard case. Pelican, founded in 1974 by a sports diver, builds waterproof cases that are extremely durable and can even be dropped in water (although Pelican advises against it) due to an airtight rubber O-ring. The iPhone-styled case also boasts an external earphone connector.On the downside, the Pelican i1015 isn't a typical iPhone case. Rather, it's mainly used for transport in watery conditions. You won't be able to call up apps while your iPhone is locked in the case, although taking the phone out of the case is easy\u2014 just snap open the latch. The Pelican i1015 sells for around $25.Traveler: Idox TravelerNot every traveler shuns hotel rooms and coffee shops for the outdoors. The Idox Traveler case envelopes your iPhone in a sleek, hard shell. With a mere flip, the case opens up into a stand for your iPhone. Watch a movie while on the stationary bike at the hotel gym or on a long flight. Or put your iPhone on your bed stand in clock mode and set your alarm for that early morning meeting.A Bluetooth keyboard would go well with this case. Unfortunately, the iPhone doesn't support one. The Idox Traveler case comes in black, platinum and pink. Price: $35.Idox TravelerRoad Executive: Incase Leather FolioRugged iPhone cases tend to add a lot of bulk to a device that's supposed to be sleek and elegant. The original cool design and simple usability of the iPhone has made the iconic smartphone popular among executives. And nothing says "executive" like a black leather holster case like the Incase Leather Folio.Made of leather and nylon, suede lining and contrast stitching, the Incase Leather Folio clips horizontally to the belt for a more comfortable fit than the vertically hanging holster. There's easy access to the earphone jack, and the iPhone can be easily drawn thanks to the "push holes" in the case.Incase Leather Folio, which costs $40, comes in an array of colors. But the combination of a black case and black iPhone looks great. Of course, this begs the question: Does anyone buy a white iPhone?Athlete: Marware Eco RunnerFor runners, functionality trumps looks. Marware Eco Runner lets runners listen to music and access apps while jogging. The case straps onto the upper arm, like a sphygmomanometer for measuring blood pressure, and completely encapsulates the iPhone in neoprene-like, non-toxic material. Thin, clear vinyl covers the screen.The Marware Eco Runner provides a comfortable way to carry your iPhone securely while sweating. The armband design keeps the iPhone and earphone wires mostly out of the way. Other cases that clip to belts aren't practical\u2014 that is, no belts on most athletic wear. An iPhone in your pocket can also fall out during a run.But Marware Eco Runner doesn't have a hard shell, so don't trip and fall on your iPhone. Cost: $35.Marware Eco RunnerTom Kaneshige is a senior writer for CIO.com in Silicon Valley. Send him an email at firstname.lastname@example.org. Or follow him on Twitter @kaneshige. Follow everything from CIO.com on Twitter @CIOonline.