Town of ZZT
From classicdosgames.com description:
"ZZT is an ASCII adventure along the lines of the famous Kroz series. The hero can move from screen to screen, fighting monsters and collecting treasures as he goes. ... ZZT is known for clever level design and use of the 16 color palette, and also uses the PC speaker to create music more effectively than most games of this era. The game also came with a level editor, inspiring thousands of user-created levels. There is still a fan following for this game even today. Epic released the full version of this game as freeware on their website in 1997."
Town of ZZT is the first volume of the ZZT series.
There are a number of cheats that work in the original ZZT to give you more health/gems/torches, and so on. You can find a list of them here on ZM (Local Mirror 12th Feb '08).
A full walkthrough for this volume by Scott Walker is available on alexandria.rpgclassics.com here (Local Mirror 12th Feb '08).
VGMaps.com hosts a number of maps by RT-55J of all the ZZT worlds. The main map for town is here - there's also one for the castle, for the labyrinth, for the prison, for the cave, for the House of Blues, for the Armory, for the bank, and for the palace.