Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Messenger for Mac - Facebook Messenger wrapped up as a desktop app
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.
Chatty - Chat with strangers all around the world in Messenger
Facebook Messenger - Facebook Messenger is a faster way to message.
Chat for Mac - Facebook Messenger & Chat on your Mac