Keybase Chat - End-to-end encrypted chat built into Keybase
Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
SafeSwiss Secure Communication - World's most secure private messaging App. Unbreakable encryption: best App for secret chat, private calls, text, SMS, video, images, data & file transfer
Crypho - End-to-end-encrypted messaging and file sharing
Zhoo - Super simple chat in your browser 💬
dPhone - The most secure calling app. Open Source and Free.