Incase Slider Case for iPhone
Incase's Slider Case for iPhone, available in glossy white or black, is very similar to the Agent 18 case, above. However, instead of two equally-sized pieces, the Slider Case uses a main piece that slides over the top of your iPhone and a smaller bottom piece. The reason for this approach is that, because the bottom of the Slider covers much more of the iPhone's bottom edge, you can't connect bottom-mounted dock-connector accessories, or place your iPhone in a dock cradle, while the phone is in the case. To get around this restriction, the bottom piece of the case is made to be easily removed. It simply slides off, giving you full access to the dock-connector port. When you're done using dock accessories, you just slide the bottom piece back on.
Although this design works well, keep in mind that if you frequently use such dock accessories, you'll find yourself removing and replacing the bottom piece of the case many, many times. Over time, this repeated wear and tear could result in scuffs or scratches to your iPhone. I did prefer the Eco Shield's design in this respect.
Another difference between the Slider and the Eco Shield is that the inside of the Slider includes two thin, low-profile silicone strips--which contact the back of your iPhone--to provide a good grip on the phone without requiring the case to fit so tightly. In theory, these strips should reduce the chances of the case actually scratching the back of your iPod due to dust or dirt inside, although the silicone does leave some marks of its own; thankfully, these marks rub off easily. (Incase also claims the strips offer some shock protection, although the strips are so thin that I would suspect the actual degree of protection to be minimal.)
I especially liked the Slider's glossy coating, which in addition to being very attractive--especially the white model--was also surprisingly scratch-resistant in my testing.