Clean and simple game that provides quite the challenge.
Porkle(2/1/2010 - version 1.5.6)
This is a beautifully rendered and extremely difficult version of Reversi. I give it 4/5 only because:
1) it makes you feel like an idiot. I would probably feel less dumb if the difficulties were labeled "hard, ludicrously hard, obscenely hard, evil, etc" but instead they are just labeled "level 1, 2, 3, etc".
2. undo/redo aren't enabled (they are just strangely present in the game menu)
3. The game crashed on exit