You have the power to master any weapon (as long as it was made to be a weapon for war)

Pistol, knife, rifle.

i go strate ol skool an use mah trustay spear

The Pen of course.
I would then use it to write something that millions would follow to do my bidding. They can use whatever weapons they want at that stage, as long as I would have their attention. Using the pen, I would draw cool pictures and write witty things that people would believe as fact, when really it would just be my personal propaganda.