Guild Wars Description
"No inherent effect. Many Pirate skills, especially those crazy schemes to get a pirate out of any mess, become more effective with higher Cunning Plan."
Cunning Plan is a very useful attribute for Pirates. It gives them many of their more well rounded skills and gives them the opportunity for various types of sneak attack. Many of the more bizarre and outlandish of the skills that the Pirate class possesses are those relating to Cunning Plan. It also emcompasses a small set of summons, such as Sea Turtles, Skeleton Crew and Naga to fight for your cause.