Dialogflow - Conversational UX Platform. (ex API.ai)
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
WhatsApp Desktop - WhatsApp, now on your desktop
Botpress - Open-source platform for developers to build high-quality digital assistants
Wafer Messenger - Endless Creativity, Limitless Reach.
Expensive Chat - Chatroom where you pay per letter