What are your favorite apps on the iPhone?

I'm curious to know what are peoples favorite iPhone apps that do just one thing ... but perhaps, do that one thing very, very well. Polarize [styles photos to look like old polaroids] is probably mine. It's quick, easy and works every time. What's you...

I just got the iTouch and I want to get some more apps! What are your favorite free apps? Thanks!

I'm deliberating getting an iPhone because I've heard it's a great phone for a high school / college student. Aside from games, what are your favorite apps? Any great school-related ones that you would recommend?

The apps can be used for anything (not Apple's pre-loaded apps), productivity, games, social networks, photography, ect...

Just looking for fun apps :) Games, resources, anything..:) Thanks!!

I got one yesterday and so far I've gotten about 50 apps. Just curious to know about good ones that I may not have yet. Thanks!

I'm currently evaluating Titanium and wondering how serious such framework can be taken to develop real high quality (especially UI wise) cross-platform apps. Looking at the Titanium showcases at http://www.appcelerator.com/show..., you mostly see apps...

I'm trying to understand what the average retention rate is on free and paid apps on iPhone and if it's better to launch a paid app because the user retention and engagement is much higher.

Are people using iPhone/Android apps for research and data collection? For example: Mappiness (http://www.mappiness.org.uk/), which aims to collect data on happiness in the U.K. It works by push notifying users for information on their happiness, location...