Yugioh

Now there are many version but I know that many will agree that the original is the best:

Yu-Gi-Oh! tells the tale of Yugi Mutou, a timid young boy who loves all sorts of games, but is often bullied around. One day, he solves an ancient artifact known as the Millenium Puzzle, causing his body to play host to a mysterious spirit. From that moment onwards, whenever Yugi or one of his friends is threatened by those with darkness in their hearts, this 'Dark Yugi' shows himself and challenges them to dangerous 'Shadow Games' which reveal the true nature of someone's heart. As the series progresses and its focus shifts to the fictional card game known as Duel Monsters, Yugi and his friends learn that this other Yugi inside of his puzzle is actually the spirit of an unnamed Phaoroah from Egyptian times who had lost his memories. As Yugi and friends attempt to help the Pharaoh regain his memories, they find themselves going through many trials and facing off against others wielding the mysterious Millenium Items.