Public - Group chats.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Chalk - Chalk is a calculator that tries to do right what others do wrong.
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.
Slaask - Slaask enables you to set up a dedicated live chat channel on your Slack.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.