Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Drift - A messaging app that helps you grow your business.
Smallchat Beta - Slack integration for chatting with visitors to your website
Drift for Enterprise - Automatically turn website traffic into sales meetings
Firehose Chat - firehosechat.com
SendBird - SendBird is messaging-as-a-service.