irssi, my favorite IRC Client.

Irssi is a terminal based IRC client for UNIX systems. It also supports SILC and ICB protocols via plugins. Below is a screenshot of mine (it's extremely plain)
                        

                                

Greatest features

You might be wondering what makes Irssi such an easy and comfortable client to use; Joost Vunderink wrote a summary of the most beneficial Irssi features.

• Autologging
  

  Irssi will automatically log any channels, queries or special windows that you want. The logfiles will be separated per IRC network, and even log rotation is supported. Log file formats, themes and destination directories can be easily configured with the Irssi log settings.

• Formats and themes
  

  Theming is a popular item in todays desktop enviroments, it's an easy yet powerful way to customize your Irssi client's look and feel. Irssi's formatting is modular which means you can just change the appearance of the objects and all items contaning that object will change into that format.

• Perl scripting
  

  Perl is one of the most used programming languages around the globe and integrating Perl into applications means flexible and powerful scripting capabilities. The entire behavior and appearence of Irssi can be modified within these Perl scripts. Irssi provides a script archive with many contributed Irssi scripts which provide both useful extra features and the required assistance to make your own scripts.

• Irssi-proxy
  
  

  This is much more than just a bouncer, Irssi-proxy is a plugin which allows to bind a port to each IRC server you are connected to. This means that instead of having to remember to identify with a password, you can just connect to the Irssi-proxy with a server password. The copy of Irssi running the proxy works just as a normal client which you can use, but you can also connect one or more clients to it to share the connections. Using Irssi as a proxy has the major advantage of Irssi's power as an IRC client. You never have to worry about losing your connection to IRC. Even if you don't want to use Issi as a client, I can strongly recommend it as a proxy because you can just connect to it with any IRC client by just connecting to the specified port instead of SSH-ing to the machine that your Irssi is running on.

 You can download irssi from here, or use the repositories.