irssi - Irssi is a terminal based IRC client for UNIX systems.
Zoom - Zoom unifies cloud video conferencing, simple online meetings, group messaging, and a software-based conference room solution.
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.
Slack - A messaging app for teams who see through the Earth!
KVIrc - KVIrc is a free portable IRC client based on the excellent Qt GUI toolkit.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.