The US Military Secret is an item in the video game No More Heroes. It is a plan Travis Touchdown obtains after his Ranking Battle against Holly Summers. The plan is taken to Dr. Naomi who combines its research with her own, to produce the Tsubaki Mk-II beam katana.
Little else is known about the contents of the US Military Secret, but it is more than likely that the United States military was researching beam katanas as well, and either found a solution to allowing the emitter and receiver of beam katanas to operate simultaneously, or founded a weapon of the same caliber. This may explain the significance of how, after reviewing top secret plans, Naomi could design the second Tsubaki prototype.