Import any weapon from any game into Call of Duty

[Jabberwock King]

Fuel rod cannon and Needle Rifle from Halo. CoD is in desperate need of color and that would certainly do it.

UPDATE: And my favorite armor ability Evade (sorry jet pack, maybe next time).

 

[Bassman_2]

Sniper with a Portal Gun or a LittleBigPlanet 2 Creatinator and a Dark Energy Blue-Colored Gravity Gun

 

[Jabberwock King]

Fuel rod cannon and Needle Rifle from Halo. CoD is in desperate need of color and that would certainly do it.