Wizard Assassin - A Harry Potter Choose Your Own Adventure by blairdiggory

Fred and George have set up a Hogwarts-wide event called Wizard Assassin. Sort of like a Hunger Games, students have to Stupefy or Expelliarmus other players to get them out, and being the last person standing wins you a whole lot of gold. And one more thing - the teachers can't know. Can you become the Wizard Assassin champion?