Sip

•ANSI-TRUE: All the colors you could hope for.
•MXP: Pictures, sounds, clickable text, and mini-frames.
•MSP: Sound and Music
•GMCP: Access server information out-of-band + Client.Login, Client.Media.
•MSDP: Access server information out-of-band
•Aliases: Customize your commands, or trigger a myriad of events.
•Triggers: Cause a custom action when the mud sends a particular message.
•Scripts (JavaScript): Go wild with customizing your mud client.
•Timers: Cause some action to occur periodically, or after a delay.
•Plugins: Sweet bundles of Modifications.
•MXP editor: Customize your screen layout or colors, have a window for TELLs, etc.