Assassins Creed, probably my favourite game series, is a game series for the Xbox 360, PS3 and PC (which also has spin-offs on Wii and handheld devices) in which you play as assassins basically killing targets which unfolds many different stories and side-quests.
Sounds simple, and to be honest it is, the game controls are very easy to get used to and at the same time it is very enjoyable as well as satisfying completing missions. It has stunning HD graphics and is definately at the top of it's league for visual gameplay and cut-scenes.
More on the stories of the games, you play as a character called Damien who is locked up in a cell, and is forced to use the 'Animus' to unlock secrets about his ancestors' past - this is obviously the starting point and as the story unfolds, a small team break him out of his cell to use his ancestors' secrets for the good of mankind's future. Anyway, no more spoilers so don't worry about that haha. But there is the highly anticipated Assassin's Creed Revelations coming out in November 2011, a game to look out for.
But honestly, I havn't encountered any game series that has such a mindblowing and gripping storyline, definately a game to buy; I rate this game 9.5/10.