Not all iPhone 4 cases are compatible with all iPhone 4 cables -- even Apple's bumper doesn't work with their own A/V cable! -- but there are several cases that work with a wide variety, including A/V, car kits, and chargers. Here are two of our favorites on the ultra-light side:
Feather is made of an ultra light, ultra strong polymer for light as a feather, form-fitting durable protection without the added bulk. Feather features a soft touch matte finish and includes 2 surface protectors and a cleaning cloth. Feather by Incipio is so thin that it allows the iPhone 4 to be used with many of the docks on the market.
The Barely There is Case-Mate's new line of sporty cases for the iPhone 4. These cases are designed to help protect the design of the iPhone 4 while allowing more of it to show. There's also a Chrome version (Georgia's favorite!) for those of you who want to add some mirror-bright bling to your iPhone 4.
Both are available now in a wide variety of colors from the TiPb iPhone 4 accessory store, check them out!