Federal Express (FedEx)

As the activist investor William A. Ackman hunts for his next target, a favorite guessing game on Wall Street is to see what company he will pick next to agitate for change.

That didn't take long. The economy hasn't yet recovered from the implosion of risky investments that led to the worst recession in decades—and already some of the world's biggest banks are peddling a new generation of dicey products to corporations, consumers, and investors.