Camera Genius (App Store, $1.99) used to be my favorite camera app, but I eventually stopped using it in favor of the stock camera app that's pre-installed on the iPhone.
On the iPhone’s Camera Plus Pro app Ha writes, “If you've jailbroken your early gen iPhones then, yes, your device is capable of recording video, but that's illegal. Heh. If for no other reason, you should purchase Camera Plus Pro just to have video recording on your Silverback or 3G. It's just icing on the cake that it comes with all the bells and whistles you'd want from a camera app.”
The full list can be found here.
Do you use any third-party camera apps for the iPhone, if so, which ones?