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
Crisp Chat - Multi-channel customer support software
Speaklyn - Website visitors chat with you on Facebook Messenger
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
WhatsHelp - Communicate personally with your customers via Messenger