Chatfuel - Chatfuel is the best bot platform for creating an AI chatbot on Facebook.
Dialogflow - Conversational UX Platform. (ex API.ai)
VECA - Your eCommerce assistant
Octane AI - Octane AI offers tools to create a bot and engage customers and audience via messaging.
ChatterOn for Messenger - Build Facebook chat-bots in under 5 minutes
Botpress - Open-source platform for developers to build high-quality digital assistants