Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
WhatsHelp - Communicate personally with your customers via Messenger
Smallchat Beta - Slack integration for chatting with visitors to your website
Chatra - Live chat software that helps to increase revenue and collect feedback providing an easy way for website owners to talk to visitors in real time.
Firehose Chat - firehosechat.com
Facebook Chat for Websites - Talk to your customers using Facebook Messenger