When pharmaceuticals giant Actavis said it was buying Allergan Inc. and Halliburton said it would take over rival oil-field servicer Baker Hughes, Wall Street rang up a rare $100-billion deal day that pushed the total value of mergers globally to more than $3.2 trillion for the year, according to banking research firm Dealogic. "This acquisition creates the fastest-growing and most dynamic growth pharmaceutical company in global healthcare," said Actavis Chief Executive Brent Saunders.