The following are the secret moves labeled as classified (and thus undocumented) in the manual:
Interceptor Missiles Halo Decoy: Up-Up-Down-Fire Machine Gun Cost: 2 Missiles
Bull's Eye Rockets Stampede: Up-Down-Up-Fire Machine Gun Cost: 5 Rockets
Sky Hammer Mortar Turtle Turnover: Down-Down-Down-Fire Machine Gun Cost: 2 Shells
Bruiser Cannon Cow Puncher: Down-Up-Down-Fire Machine Gun Cost: 2 Shells
Roadkill Mines Cactus Patch: Left-Right-Up-Fire Machine Gun Cost: 2 to 6 Mines