Beat every mission on a certain difficulty to unlock the corresponding weapon.
Zero Laser Rifle - Beat all missions on Easy. ZE Launcher - Beat all missions on Normal. Y20 Impulse - Beat all missions on Hard. PX50 Bound Shot - Beat all missions on Hardest. Genocide Gun - Beat all missions on Inferno.
Achievements
Complete each achievement to get the allotted gamerscore.
All Stages Cleared (Easy) (50) - Clear all stages on easy difficulty. All Stages Cleared (Normal) (100) - Clear all stages on normal difficulty. All Stages Cleared (Hard) (150) - Clear all stages on hard difficulty. All Stages Cleared (Hardest) (200) - Clear all stages on hardest difficulty. All Stages Cleared (Inferno) (300) - Clear all stages on inferno difficulty. All Weapons Aquired (200) - Aquire all weapons.
