This is the quickest way to unlock new weapons in Modern Warfare 3 right now

techradar.com:

Although we were very underwhelmed by the content of the single-player campaign, the new multiplayer zombies mode in Modern Warfare 3, titled Modern Warfare Zombies, is an unexpected delight and boasts a brilliant bonus for anyone trying to get their hands on the game's new weapons.

An open-world take on the classic Call of Duty zombies formula that offers a huge environment to freely explore with your friends, Modern Warfare Zombies feels like the perfect evolution of Modern Warfare 2’s already compelling DMZ mode. 

Borrowing elements from the extraction shooter genre, which has been shaped by hardcore titles like Escape From Tarkovand Hunt: Showdown, your main objective in this mode is to complete challenges in the open-world and then successfully extract with your squad in order to keep the rewards.

Unlike other modes, your loadout is very restricted here and consists mostly of items that you have scavenged from the map. Interestingly, however, playing Modern Warfare Zombies is currently the quickest way to get your hands on many of the new weapons that have been added in Modern Warfare 3.

This is because weapons that you extract with are automatically unlocked across the rest of the game — including gear that you haven’t managed to acquire through the normal leveling process. This means that you can get your hands on high-level weapons early.

I, for example, was able to unlock the powerful new revolver, the TYR, in about ten minutes rather than having to grind for hours in order to reach level 50 where it normally becomes available. This was accomplished by simply finding the weapon at a weapon buy station on the map, purchasing it with currency that I had gained from slaying undead foes, and then booking it to the