WeChat by Tencent Technology (Shenzhen) Company Ltd.
As of June 2013, WeChat rank number 1 at Google Play Top Free App (play.google.com).
What makes it to that position?
TV commercial ads could be the main reason why WeChat attain its position right now. They already launched their TV ads at different countries including Hongkong, USA, Indonesia, Malaysia, Mexico, Philippines, Singapore, Thailand.
Philippines: Iya Villania and Drew Arellano