I always enjoyed Shadows over Camelot, for you have to work towards your own goal as well as working together as a team.

Then, when you are more accustomed to the game, you can include a player actually being a spy that covertly has to sabotage the group while still pretending to be doing good.

Link

And a part of the description for those who hate clicking links:

Each player represents a knight of the Round Table and they must collaborate to overcome a number of quests, ranging from defeating the Black Knight to the search for the Holy Grail. Completed quests place white swords on the Round Table; failed quests add black swords and/or siege engines around Camelot. The knights are trying to build a majority of white swords on the Table before Camelot falls.

On each knight's turn, the knight takes a "heroic action", such as moving to a new quest, building his hand, or playing cards to advance the forces of good. However, he must also choose one of three evil actions, each of which will bring Camelot closer to defeat.

Moreover, one of the knights may be a traitor, pretending to be a loyal member of the party but secretly hindering his fellow knights in subtle ways, biding his time, waiting to strike at the worst possible moment...