Messenger Video Calls - Facebook Messenger, now with HD video calls
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
HelpScout - Help Scout is a simple, straightforward way to provide excellent support
Quickie - 3-60 second video calls with your friends
GoSquared Live Chat - Beautiful, simple, and free live chat for your website