There's something disturbingly fascinating about characters whose job it is to take lives. If you're an anime fan who needs a little more hitman action in your life, you should know that there are some fascinating anime where the protagonist is an assassin.
Some, like the shonen hit Assassination Classroom, manage to be fairly cheerful and wholesome despite their content. Other shows, like Darker Than Black, are as gritty and intense as the subject matter implies. No matter what your taste in hired executioners, you're sure to find something on this list that appeals to you.