The NuGuard KX iPhone case is the latest we've received that proclaims that it's MILITARY DROP TESTED (a/k/a conforms to MIL-STD-810). NuGuard advertises "X-Orbing gel" technology that allows their case to offer that protection without a complicated set of parts that need careful assembly.
The case promises that protection for the iPhone 4/4s and iPhone 5/5s with a lot less bulk than its competitors. There's a wide array of colors and the prices range from $25-$29 when you buy direct from the Other World Computing site. The cases are also available for the Samsung Galaxy S4, the iPhone 5c, the iPad Air and iPad Mini.
Pair that with the NuGuard KXs screen protector ($14.99) and your phone should be able to pass the hammer test.
We tested out a case on an iPhone 4, replacing an Otterbox whose silicon outer case had worn out and ripped from everyday use. The NuGuard case doesn't have multiple layers to rub against each other and it's easy to remove if you're inspired to swap it out. It's not as heavy-duty as some of the other cases we've used, but it's also a lot less bulky. If you're not using your phone in extreme conditions, this case will provide good protection against the kind of everyday parking lot drops most of us face.