One Piece follows the story of Monkey D. Luffy, a teen with dreams of becoming the King of Pirates. In order to do this, he will have to sail the Grand Line looking for the legendary One Piece, the largest treasure stash in the world. Imbued with the powers of the Gum-Gum Devil's Fruit, Luffy has the ability to stretch his body to unusual lengths. Throughout his adventures, Luffy acquires new crew members Zoro, a master swordsman; Nami, an expert navigator; Usopp, who's not really good at anything; and Sanji, a cook who only uses his legs and feat in combat (because he feels a cooks hands are to valuable to waist on hitting people).
One Piece is highly adictive due to its awsome story, unique art style, and detailed characters. I suggest that you read it at one point or another. Volumes 1-3 of the manga are available in english, with vol. 4 coming out soon.
I took a character quiz for One Piece, and this is who I got: