You can use an unlocker, or do this through .gsc modding.
I'd say do the first one.
I never use trainers/unlockers so couldn't recommend you any, but I'm sure you'll find what you're looking for if you look in the general cod:mw2 hack forum
Hey there i just want to ask if there is any code that only give like "lightwieght pro" so that you dont have to run or complete all challenges to get it.
I mean for a mod not for my only for my self but for everybody else in the lobby.