There are many apps available for messaging but I will answer as per your questions. The best apps available for messaging other than Whatsapp are as given below:
Kik is one of the best app for messaging. Kik app is available for most of the platforms like iOS, Android, and Windows Phone operating systems. It is available in free of cost so that it can have more and more users. There are many Indian users of this app as this is an awesome app. It was modeled after BBM. It uses the Internet data to send messages and to receive messages. As per my own experience this is an awesome app and I also use it.
It is also one of the best app available for smart phones for messaging. This app has many of the awesome features in it like the users can send texts, images, videos, audios, voice messages and many more. It was launched on 12th December, 2012. It has many of the users.
It is a photo messaging application with many of the Indian users. Using the application, users can send photos, videos, text and drawings, to their friends if they use this awesome application. Many of the users use it daily.
As per my opinion Skype is the best app for video chatting. You can get this for free on your Google play store and you can do video chatting with your friends if they use this application. It also have many of the users. You can just talk to anyone if you know his/her skype ID.
Viber is used for sending voice messages. This app is available for many of the platforms like Mac OS, Android, BlackBerry OS, iOS, Series 40, Symbian, Bada, Windows Phone, and Microsoft Windows so that it can have many users. It works on both 3G/4G networks.
You can use any of the app from the list mentioned above as they all are just awesome with many of the users. You can get any app from the list mentioned above from Google play store for free of cost.
I find that the harder I work, the more luck I seem to have.