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. At any moment, the user can 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.
ErisMUD is a MUD/MOO server/engine written in Python and supports many features: rooms, NPCs, items, player skills and stats, ANSI colors, a help system, damage/healing, etc. SQLite is used to store the data, so no files are required for building (unlike LPMUDs). Short and easy internal commands take care of the development and maintenance.
Battletech MUX is an Internet based, real-time rendition of the popular Battletech board game. Players take to the front lines in their very own mechs, tanks, and similar implements of destruction. Featuring an internal scripting language called SoftCode, game admins may sculpt their sites into whatever they can imagine, be it small-scale combat or massive, galactic conflict.