STANLEY O'NEAL

Proved as head of U.S. private-client services that he can strategize and cut expenses. But has ruffled the feathers of some of the firm's 15,000 brokers and must regain their loyalty.JEFFREY PEEK

The head of asset management energized the firm's once-lackluster mutual-fund business. Has to show he can apply the same skills to all of Merrill's business units.THOMAS DAVIS

The investment-banking machine he runs now brings in two-thirds of the firm's earnings. Whether he has the leadership skills to run the whole outfit remains a question.