At the main menu, hit x, left, triangle, square, x, select.
All missions
Press X, L2, Triangle, R2, Select at the title screen to unlock all missions.
All special features
Press L1, L2, R1, R2, X, Select at the title screen to unlock all specials features.
Awards and Medals
Purple Heart: Get wounded or killed in action.
Bronze Star: Get 15 kills
Silver Star: Get 20 kills
Distinguished Service Cross: Get 25 kills
Congressional Medal Of Honor: Get 30 kills
Invincibility
Begin a mission, then pause game play. Press L1, R2, L2, R1, Select to become invincible.
Mission Co-operation And Firefight Co-operation modes
Beat the game and save. Now start with the saved file. Go to Multipalayer and you'll notice that there're Mission Cooperation and Firefight Cooperation modes availible in Multiplayer.
Note: In Ghost Recon there are two different games: Ghost Recon and Ghost Recon: Desert Seige(DS) (used to be sold seperately.) After you beat the Ghost Recon (15 Missions), there will be 8 new missions(for Desert Seige).