Which applications are the best with your iPhone?

Hi everybody, most of us use iPhone and this makes our work just so easier. I cannot just go out without mine! I would like to start this thread with the object of knowing the best applications that you people have come across for your iPhone. There may be some that you use quite often, most of us may be using applications related to our work and some that make things easy. Which one do you use?

I mostly use the iPhone Chat and the Collage ones. The chat is just fabulous as it helps me to keep in touch with my contacts. Another one which I found quite useful was CarSpotter which is a vehicle locator that uses the iPhone’s navigational GPS system. The application features a built-in camera, photo log, audio recorder, and text notes - in case users need to snap a shot of a nearby landmark or jot down a note about the parking meter limit. It is just good for anyone that needs to manage their car in the parking lot and is handy for most of us.