Moria or UMoria A terminal based role-playing game that probably ensured thousands of students didn't get any sleep while they were at University. Also see angband. Incredibly the game had no graphics and used text characters to represent a map of the world (which happenned to consist of six or eight shops and an endless dungeon with multiple levels which were randomly generated every time you switched levels.
Now made to look pretty pittiful by the likes of Doom and Quake