Public - Group chats.
Viber Communities - Group chat with up to 1B members, admin controls and more
chitchat - Chat Room with Selfies and Pagers (yes, pagers!)
Slack - A messaging app for teams who see through the Earth!
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
Wire - Private & Secure Messenger