Successfully complete the game with various ranks and difficulty settings to unlock additional starting weapons.
Easy difficulty, 'A' rank: All handguns and shotgun.
Easy difficulty, 'S' rank: All weapons except charged particle rifle.
Recommended difficulty, 'A' rank: All weapons except charged particle rifle.
Recommended difficulty, 'S' rank: All weapons except charged particle rifle with unlimited ammunition.
Extreme difficulty, 'A' rank: All weapons except charged particle rifle with unlimited ammunition.
Extreme difficulty, 'S' rank: All weapons with unlimited ammunition.