WhatsApp Messenger ($0.99)
Breaking the barriers between platforms, WhatsApp is a simple
messenger that allows you to send messages, audio, photo, or video files
to contacts — as long as they also have the app. What’s the big deal?
It’s completely free to send messages and the app simply uses your
network or Wi-Fi connection. It works on iOS, Android,
BlackBerry, Windows Phone, and Symbian. This is a real money saver and
it’s especially good if you want to send messages internationally. All
you have to do is get your friends to play ball.