There are a lot of companies making bumper cases of all different types but RearthUSA has something a little different to offer; a product they call the Ringke Steel Bumper. This is the first one of this type that i've seen and I will go into a little more detail later.
The Ringke is a bumper case composed of 3 separate pieces. You will first take the silicone bumper and fit it around the edge of your phone, next, take the top stainless steel frame and fit it on top of the silicone bumper, lastly, you will take the bottom stainless steel frame and fit it onto the silicone bumper and ensuring the 2 hooks lock into the 2 holes that are in the top frame piece. It will take some pressure to compress the silicone bumper enough to get the hooks to lock in place, but this will ensure a nice, solid and tight fit to the case.
With the case installed, the phone does not feel overly bulky and is surprisingly slim (adding 1.3mm to the thickness). There are 2 separate versions of this case; one that is specific to the iPhone 4 and one specific to the iPhone 4S. The case extends onto the screen and back glass providing lay on the table design with no worries of scratching your screen. The case features a cutout for the silent switch, silicone buttons to cover the volume buttons, a smaller cutout for the headphone jack and secondary mic, a silcone covering for the sleep/wake button and 3 separate cutouts for the 30 pin dock connector/mic/and speaker on the bottom of the iPhone. The cutout for the 30 pin dock connector is relatively small and I believe some aftermarket connectors would cause you problems. With that being said, the case is pretty slim so you may be able to compress the silicone enough to make aftermarket connectors work. The headphone jack on the other hand, will give those of you with large headphones (with the large plug) issues as you won't be able to get it to fit without an adapter.
I was impressed by the unique style of this case and I'd definitely recommend it. With the case, they also provide front and back screen shields, a squeege card, microfiber cloth, a lanyard and an installation tool that will help get the silicone to lay flat on the screen with the frame installed. The case as you see here runs $29.99 and is available in 10 different colors. RearthUSA also offers (as options) audio caps and dock caps for $1.99 and $2.99 respectively.