AC Brotherhood
This is the best Assassin's Creed so far. If you liked AC2, then you'll definitely like this one. Rome is a beautiful city and a lot of fun to run around. The multiplayer is fun and really extends play time.
The jack-in-the-box included is a lot of fun for scaring guests! The extra single-player maps aren't much to talk about, just a place to get some extra florins, and not really a significant amount. However, the Officer multiplayer character that comes with them is a brutal killer and fun to play with.