In Brink for the PS3 and Xbox 360, the unlockable weapons in the game can be unlocked by playing through the four different challenges.
Some weapons aren’t available to all body types, like the heavy guns (EZ-Nade, Gotlung Minigun, etc) are only available to heavy body types. Some weapons are available as a primary or secondary to certain body types, so your body type is very important depending on the types of guns you want to use.
Here is the list of weapons you can unlock, and what challenges you need to complete to unlock them.
Be More Challenge
One Star Challenge – Lobster Grenade Launcher
One Star Challenge – Ritchie Revolver
Two Star Challenge – Bulpdaun Submachine Gun
Escort Duty Challenge
Two Star Challenge – EZ-Nade Auto Grenade Launcher (heavy type only)
Parkour This Challenge
One Star Challenge – Barnett Light Rifle
Two Star Challenge – Belgo Machine Pistol
Tower Defense Challenge
One Star Challenge – FRKN-3K Assault Rifle
Two Star Challenge – Gotlung Minigun (heavy type only)