Former owners of a C64 certainly will remember Sword of Fargoal. It was created by Jeff McCord and released for the C64 by Epyx in 1983. It is a simple rogue-like game (preceding the first official release of Rogue though). And according to http://www.cdaccess.com/html/pc/150best.htm,
it is one of the best 150 games ever. A summary of its description could read like this:

You are on a quest to retrieve the Sword of Fargoal, which lies between
levels 15 and 20 of a dungeon. The dungeon levels are populated by an
ever-regrowing number of different monsters, the deeper the dungeon level,
the stronger the monsters. By retrieving experience points and collecting
treasures, your own strength will increase as well, while finding your way
down through randomly generated dungeons. With the help of different items
and all sorts of spells, and by escaping various kinds of traps, you
finally can find the Sword of Fargoal in the middle of a labyrinth - which
doesn't mean your done, no way, now the game only really begins. A timer
is started, and you have to get back up to the dungeon entrance again
before time runs out. This isn't as easy as it sounds, because dungeon
levels are newly created and look different every time you climb up or
down, and are now full of monsters waiting to steal the sword from you -
in which case you have to climb down and find it again - but the timer
isn't reset.

For more informations and the complete story, visits these sites:

http://www.fargoal.com/
http://home.arcor.de/cybergoth/epyx/swordoffargoal.html
http://www.the-underdogs.info/game.php?id=4527