mIRC - mIRC: Internet Relay Chat client
irssi - Irssi is a terminal based IRC client for UNIX systems.
HexChat - HexChat is a fork of XChat with bug fixes and new features.
WeeChat - WeeChat is a fast, light and extensible chat client.
Bidbar - Save and run Terminal commands from the Mac menu bar
KVIrc - KVIrc is a free portable IRC client based on the excellent Qt GUI toolkit.