WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Voxer - Turn your phone into a Walkie Talkie. Don't waste time on phone calls and voicemails.
Zulip - Chat for distributed teams. Zulip combines the immediacy of real-time chat with an email threading model. With Zulip, you can catch up on important conversations while ignoring irrelevant ones.
WowApp - Wowapp is the best alternative to Skype and you will get paid to use it!
Dasher Messenger - Dasher lets you do more than just text message. It's messaging with benefits: