Best iPhone apps?

I just downloaded Cycorder, which allows video recording. It's not the best recording but it's about the same as any camera on any other phone.Also, I got this program that let's me transfer files to and from the iPhone so I can take the videos from the directory and put them on my computer. Youtube here we come!Any other really good iPhone apps that are MUST HAVES?

Only App that I overuse is Tap Tap.