WhatsApp is best messaging app among the all Messaging Apps ever existed, so far I think. It is best just because of its simplicity and ease of use, and the another best thing is that its free to download for anyone.I also liked the new feature of end to end encryption in the app. The User Interface of this app is also awesome.
One of the important thing is that the app uses minimum data for its use. It works really good even if you have slow internet speed.Its really hard to live without WhatsApp, it is that best.My only suggestion is that, just never stop using this app.