How do I convince my parents to let me get M rated games?

Because I really want stuff like Fable 2, Halo3, Call of Duty 4, Gears of war. I mean it's not like I have movie like saving private Ryan, all three Terminators, the first 2 Godfather movies, The Pion Of The Christ. I know every curse word in the book, people say them all the time in school. (-_-") I have never got in trouble before...