I have a number of my own applications in the App Store, as well as many written for other clients and friends.
They are a fairly diverse mix of business and productivity tools, tracking/gps, entertainment and some are highly specialised for a particular field or business.
iPhone Web applications
Distribute your applications to everyone without having to go through any approval process. Offline capable so users don't need to have an internet connection in order to use your applications. You can then synchronise data when they do have an internet connection, to keep your application updated.
Native iOS (iPhone, iPad and iPod) development and rapid prototyping
The iPhone SDK provides the tools and resources needed to create native iPhone applications that appear as icons on the user’s Home screen. Unlike a web application, which runs in Safari, a native application runs directly as a standalone executable on an iOS–based device.