Caprine - Elegant Facebook Messenger desktop app
Linkello - Video calls simplified, no installation required.
Facebook Messenger - Facebook Messenger is a faster way to message.
jTorchat - jTorchat stands for Java Torchat, and is a complete rewrite of the popular p2p IM messenger Torchat
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Facebook Messenger Kids - Safer and More Fun Video Calls and Messaging