BarnOwl is a curses-based instant messaging client supporting the Jabber, IRC, AIM, and Zephyr protocols. It is designed to be easily extensible through Perl plug-in modules, and much of the core functionality is provided by such modules.
qwebirc is a fast, easy-to-use, Web-based IRC client. It supports SSL, tab completion, UTF-8, control codes (for colors, bold, and other text attributes), clickable channels and nicks, notifications, and many more features.
Yaaic (Yet Another Android IRC Client) is an Internet Relay Chat (IRC) client for Android devices. It features multi-server/channel support, colored text, fancy icons, smooth channel scrolling, many commands, many supported charsets, and more.
Pidgeon is an IRC client which supports various bouncers, including its own bouncer which is able to synchronize timestamps (pidgeon sv), supports the quassel core, and supports the tcl scripting engine.