Dungeon Master
I found Dungeon Master today, so I decided to buy it.
Much like Eye of the Beholder, it's one of those games I love and hate at the same time. It has massive cheeze factor and the controls are challenging, but it's so classic and neat.
It's kinda funny how games like these have inspired modern wonders like Baldur's Gate, despite the fact that I still haven't beaten EotB.