Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.

Seald - Keep your conversations secure, everywhere.

tawk.to - tawk.to is a free live chat app that lets you monitor and chat with visitors on your website or from a free customizable page

Keybase Chat - End-to-end encrypted chat built into Keybase

JivoChat - JivoChat is a live chat that enables you to talk to visitors on your website

Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.