Orcs Must Die!. You hate orcs, sure, but those $10 could be spent on something practical, like gas.
This weekend though, Orcs Must Die! is only $2.50 over on Steam, and when a video game costs less than a gallon of fuel, all financial guilt associated with its purchase is essentially eradicated. Similarly, Orcs Must Die 2 has had 10 percent brutally chopped off its pre-order price -- think of it as an investment in a sustainable future-hatred of orcs. Investing is what grown-ups do.