Before you tell me I am, I am not a CoD really devoted fan. If that was the case, my copy of Black Ops/MW2 wouldn't be gathering dust in the attic. But, I will give Treyarch this. The wonder weapons are kickass, and they fit Fallout's "futuretro" theme perfectly. All of them work, but the Raygun above all.
http://callofduty.wikia.com/wiki/Ray_Gun
The reload animation places something that looks not unlike a Energy Cell/MFC inside the chamber. Could work? And also, the Thundergun is the Energy Weapon 'shotgun' the game needs. Multiplas/Tri-beam are too tight to be considered shotguns to me.