Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Smooch.io for Facebook Messenger - Message your customers from Slack, Front, a bot or anywhere!
Live Chat by Sumo.com - Instantly communicate with customers, prospects & visitors
It's Alive - Create a Facebook bot in minutes
GoSquared Live Chat - Beautiful, simple, and free live chat for your website
Drift - A messaging app that helps you grow your business.