KildClient is a MUD Client written with the GTK+ windowing toolkit. It supports many common features of other clients, such as triggers, gags, aliases, macros, timers, and much more. But its main feature is the built-in Perl interpreter. You can at any moment execute Perl statements and functions to do things much more powerful than simply sending text the the mud. Perl statements can also be run, for example, as the action of a trigger, allowing you to do complex things. Some built-in functions of KildClient allow interaction with the world, such as sending commands to it. KildClient's ANSI support s extensive: it supports not only the common 16 colors, but also supports underlined text (singly and doubly), text in italics, text striked through, reverse video and "hidden" text. It also supports vt100's line-drawing characters, and xterm's escape sequences for a 256-color mode. All these features make KildClient one of the clients with the most features for displaying the mud output. It supports MCCP versions 1 and 2, and chat using the MudMaster and zChat protocols. See the features page for a more detailed list of features.
If you'd like to see KildClient in action, be sure to check out some of the screenshots.
You can get latest version of KildClient from the downloads page.