Another from the LD bunch I liked, imagine a 2d maze game where you have to go around rocks and have to avoid pits to get the diamond. Now imagine that there are more than 1 of those caves on screen with different designs, and rotated in 90 degree increments. When you make a move, all characters move at the same time.
Ok, I really have to admit that (like sh3) after it showed 3 caves at once, my brain began to melt! But for 48 hours, it's brilliantly executed :)