HexChat
HexChat is an IRC client based on XChat, but unlike XChat it’s completely free for both Windows and Unix-like systems.
WeeChat
WeeChat is a popular, fast, light and extensible chat client, with a text-based user interface.
mIRC
mIRC is a popular Internet Relay Chat client used by individuals and organizations to communicate, share, play and work with each other on IRC networks around the world. Serving the Internet community for over two decades ...