Irssi is a modular IRC client that currently has only text mode user interface, but 80-90% of the code isn't text mode specific, so other UIs could be created pretty easily. Also, Irssi isn't really even IRC specific anymore, there's already a working SILC module available. Support for other protocols like ICQ could be created some day too. Note: this is not official version, this is svn snapshot, so it can work unstable in some cases.