Overlord: Raising Hell
Not to sound wishy-washy about the Raising Hell expansion - because I definitely am - but the last level brought my opinion of it back down to "meh." More confusing level design and arbitrary puzzles, culminating with a boss fight that is basically impossible until you discover what you're actually supposed to be doing (or, look it up in a guide).
As I've said before, the humor is great; plus, the final scene of the expansion sets the stage for Overlord II's diminutive overlord. So if you're in love with the Overlord mythos, Raising Hell is a good way to spend a few hours. But it doesn't offer anything of substance that you can't already find in the main game.
Progress: Complete