OMG!! LOOOOOOOOOL!
I saw this thread title and IMMEDIATELY thought about Rogue! I was all like, that was a bad-ass game.. I'm going to say Rogue! Then I thought, damn.. no one is going to ever have heard of Rogue and I'm going to look like a tool. Haha!
Then I scroll down and see your post...
Rogue was simplicity personified... and HIGHLY addictive! Many hours did I lose playing that game. Even got most of my friends addicted to it and we had competitions to get the high score. You would get down to the lower levels and start freaking out. OMG it's a "D"!! And a "V"!!
http://en.wikipedia.org/wiki/Rogue_(computer_game)