Successfully complete the indicated task to unlock the corresponding equipment:

Ambassador gunship: Successfully complete level 3 of the Helicopter Flying mission.
Carpet Bomb: Check Commander Leviathan's job list before the final Allies or China mission. Complete the job to unlock the Carpet Bomb for purchace.
Diplomat heavy tank: Destroy the targeted buildings for the Allied Nations.
MOAB bomb: Successfully complete all HVT missions for the Allied Nations.
Nuclear Bunker Buster: Successfully complete the final contract mission, "Get Solano Part 2" to unlock it for purchase from Eva for $1 million.