irssi - Irssi is a terminal based IRC client for UNIX systems.
mIRC - mIRC: Internet Relay Chat client
LimeChat - LimeChat is an IRC client for Windows, Mac OS X and iOS. Features
HexChat - HexChat is a fork of XChat with bug fixes and new features.
WeeChat - WeeChat is a fast, light and extensible chat client.
Kiwi IRC - A hand-crafted IRC client that you can enjoy. Designed to be used easily and freely.