The latest in Ubisoft's popular Rainbow Six shooter franchise, Tom Clancy's Rainbow Six Vegas 2, has already shipped over one million units in the U.S., according to the most recent investor research note on the publisher from Wedbush Morgan Securities' Michael Pachter.

The game hit store shelves only one week ago and has been garnering positive reviews (over 83% on GameRankings.com), including a solid 8-out-of-10 from GameDaily.

Pachter previously estimated that 1.7 million units of the game will ship for the current quarter, and he acknowledged that these early results for the game "compare favorably" with his estimate. He also noted that Ubisoft's U.S. retail sales are up 26 percent quarter-to-date compared with the company's guidance for a revenue decline of 18 percent in the current March quarter. "We expect the upside in Rainbow Six to offset weakness caused by the strong Euro and lighter performance of its other releases (notably LOST) during the quarter," Pachter said.

The Tom Clancy games continue to be a big driver for Ubisoft's business, and the publisher recently made sure the brand stays with Ubisoft indefinitely, locking up all rights to the Tom Clancy name, including books, movies and merchandising products, in addition to games of course.