I'm obsessed with debt shenanigans and, in particular, the emergence of an entire industry (or so it seems) of lawyers who specialize in finding and exploiting contract loopholes in places where the parties to the transaction had no idea there were gaps. And there are others who defend against this. (Anyone remember J.Screwed or Windstream?).
One area where the payouts of successful loophole detection and exploitation has shown big returns is the world of Private Equity.