Ueki no Housoku

The story starts out with the Battle of the Supernatural Powers, a tournament to decide which Celestial (heavenly being in the original Japanese version) will be the next King of the Celestial World (God in the Japanese version). Each of the 100 King Candidates (God Candidates in the Japanese version) is required to choose a junior high school student to act as their power user. The student is given a unique power and told to eliminate as many enemies as possible. The winning King Candidate will become the new King of the Celestial World and the winning student will receive the Blank Talent (Black Zai in the Japanese version), a talent that can be anything they choose. While this leads many students to thoughts of greed and selfishness, Kosuke Ueki decides to take it upon himself to win this tournament to keep that power away from those that would abuse such a gift. (Source: Wikipedia)