AK-47, its easy to manufacture, its reliable and its very effective
There's no such thing as the best weapon. You can only define the best weapon for a already given situation. The best weapon is the one that allow you to utilize your army as a whole. But one weapon is never enough.
The lance.
The roman army did not use nuclear weapons.
The Whipper is the best weapon for Wyplash.
It stands for Army laser weapon simulation
Mp5, AK47
the best weapon is a bow and arrow
The best weapon is to cut people
In some countries which field it, it's operated as a crew served weapon. However, in the US military, it is fielded as an individual weapon.
The overall best weapon is the Plasma Cutter. This is the first weapon you will acquire in the game.
There is no best weapon. Every weapon can be used in the best advantage depending on your situation.
Army and Marines.