My parents are strict on games

Can anyone give me advice on trying to convince my parents to let me buy a game thats 18 when im 15. I want to buy modern warfare two and fallout 3 but they are both 18. Help me!!!
Any tips please!!!

lol just give one of your friends older bother or sister the cash and they will get it for you! luckily my parents dont care, so I've been playing rated M games sense I was 7

or he could go with the Honest approach and ASK them.
telling them in the process that it's only a game and is a good way to show he is Responsable(spl) enough to play a Violent game and to Understand why He would'nt ever copy the games actions with his own in real life.

Tell them its just a basic war shooting game, there is no sex scenes or horrible acts of mutilation, in my opinion a 5 year old can play this game without getting scared or being tainted. Its just a shooting game.

^ I dont think a 5 year old could even have the patience to play long enough to get to the Violence.
10 seconds after trying to do The Pit portion of the first level in MW2, they'll be like BORING NEXT!!!