Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Dialogflow - Conversational UX Platform. (ex API.ai)
blockslack.io - Chat for small teams — encrypted and decentralized
Expensive Chat - Chatroom where you pay per letter
Botpress - Open-source platform for developers to build high-quality digital assistants
Magic Chat - Texting app that predicts your needs.