HexChat - HexChat is a fork of XChat with bug fixes and new features.
irssi - Irssi is a terminal based IRC client for UNIX systems.
IRCCloud - IRCCloud is a modern IRC client that keeps you connected, with none of the baggage. Stay synced and notified wherever you are with our web and mobile apps.
Kiwi IRC - A hand-crafted IRC client that you can enjoy. Designed to be used easily and freely.
KVIrc - KVIrc is a free portable IRC client based on the excellent Qt GUI toolkit.
Quassel IRC - Quassel IRC is a modern, cross-platform, distributed IRC client based on the Qt4 framework.