XChat

Xchat is a popular free IRC client for Unix and Unix-like operating systems. It is released under the GNU General Public License.

It has a graphical user interface, which uses the GTK+ graphics toolkit, which in turn is based on the X Window System.

It uses tabbed windows[?] for irc channels.

It allows Perl, Python and binary (usually C) plugins.

Homepage: http://www.xchat.org