What is the one app you really can’t go without?

What does it say about you?

We want to know if it is something like messaging or email (Outlook or GMAIL), games (Angry Birds, Temple Run, etc.), or social (Facebook, Google Plus, Twitter, etc.).

Why? When choosing to develop applications, it is important to know where the demand is. Otherwise, you are spending resources that would be better spent on other projects. So, as a business, it would be really great to get some feedback and see what really matters to users out there.