According to Examiner and based on the reports of a GameStop store manager who saw a MW2 demo, there are quite a few goodies in store for the upcoming release, including the already talked about dual-weapons. However, the multiplayer mode was the surprise, in which the in-game characters can now use riot shields to recover fallen teammates! For the Xbox 360 owners it will apparently not be such a big surprise since it seems that it looks and acts very similar with the GoW2 shield.
Also, during the demo, the source noticed that now knives can be thrown at enemies, and that is certainly a nice addition that will add some extra flavor to the game.
The same will do the Perks system, of which there are three confirmed perks: the already mentioned Riot Shields, Martyrdom and Akimbo (the dual-weapon wielding system). However, fansite Modern Warfare 24/7 posted some new possible perks, like a stopping power perk, a heartbeat sensor, a speed perk and two more that are tough to identify. I am sure we’ll have more on them from Activision themselves, as soon as they have them all figured out.