There have been some major exploits done in MW2, but all have been glitch unitl now. One man army, a perk alownig the user to switch classes during gameplay,pro version-faster swaps. People have been using noob tubes(grenade launchers) with OMA and are learning how to shoot their noob tubes in "hot zones." You may think this is harmless and will never get any kills, but the person can get a flawless by standing in one spot or even get a nuke by standing where they spawn. This has been a problem unlike scavenger because the person doesn't need to move, just bring out OMA and pick their class.
Some of the more popular MW2 community players have started protesting the use to OMA or to update the game to limit this perk. We will have to see what #fourzerotwo, Rober Bowling Infinaty Wards Community director and game designer, will do about this problem and how they will fix this.
