Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Talkus - Chat with your website users from Slack
Drift - A messaging app that helps you grow your business.
Chatlio - When you have a business to run, your average instant messaging software just will not do. You need an internal presence upon which your entire team can collaborate on. Read more about Chatlio.
Crisp Chat - Multi-channel customer support software
HeyHi.sg - Video call with interactive whiteboard