Assassin's Creed is a new action/adventure game from Ubisoft Montreal scheduled for Q3 or Q4 of CY2007. It is developed by members of the Prince of Persia: The Sands of Time team.
The game's events take place in 1191, during the Third Crusade in the cities of Jerusalem, Acre, and Damascus. The player takes the role of an assassin named Altair from an organization called the Hashashin whose goal is to assassinate the architects of the Crusades. The game will feature very interactive environments and historically accurate cities. Non-player characters will react to how you control your character. One example is climbing a wall may result in civilians gathering to watch, which will then attract guards.
The game also features free-roaming environments where the player can climb nearly anything--exploring cities from rooftops with scale possibly rivaling The Elder Scrolls IV: Oblivion and Grand Theft Auto games. Combat in Assassin's Creed will be more realistic in that characters will weaken as they are hurt and they cannot survive repeated blows from a sword. The game will also feature a new concept called "social stealth." Rather than stealthily sneaking in the shadows, the player can blend into the crowds after assassinating someone in public.
The title sold:
December 2007: 893,700 copies (US) (Source)
November 2007: 980,000 copies (US) (Source)
Also see Assassin's Creed (PS3).