Top 10 Mobile Apps - WhatsApp

  WhatsApp OS: [iPhone, Android, Windows Phone, Blackberry, Nokia]
WhatsApp Messenger is a cross-platform mobile messaging app which allows you to exchange messages without any cost. WhatsApp uses the same internet data plan that you use for email and browsing, so you can be with your friends and loved ones with no cost. Other than messaging, WhatsApp allows to have groups, share images and videos and audio messages as well.