Conversations.im - XMPP client designed with ease of use and security in mind
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
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.
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
Pidgin - Pidgin is an easy to use and free chat client used by millions. Connect to AIM, MSN, Yahoo, and more chat networks all at once.