Potato MU* Client, by Mike Griffiths, is a popular graphical MUSH/MUD/MOO/MU* client written in Tcl/Tk, and currently one of the most actively-maintained MUSH clients.
MG: It was originally started as a very basic client by a friend of mine, who named it Potato (so don't blame me for that;) and I've re-written it twice now to expand the features, and (the second time) to clean the code up and update it to Tcl 8.5.