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.
Firehose Chat - firehosechat.com
Talkus - Chat with your website users from Slack
Speaklyn - Website visitors chat with you on Facebook Messenger
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.