Unlock the following masks by performing the corresponding tasks:

MASK - HOW TO UNLOCK
Big Boss - Get the big boss emblem. When you wear this mask, it causes enemies near you to cower in fear and/or run away screaming.
Crying Beauty - Defeat crying beauty without killing her.
Drebin - Get over 60 weapons.
FaceCamo - Defeat laughing octopus. This mask functions like the octocamo suit, but just on your head.
Laughing Beauty - Defeat laughing beauty without killing her.
Metal Gear Solid Snake - Start the shadow moses level.
Otacon - Hit otacon with the metal gear Mk. II during an interactive mission brief.
Raging Beauty - Defeat raging beauty without killing her.
Raiden A - Hit sunny with the metal gear Mk. II during an interactive mission brief.
Raiden B - Hit naomi with the metal gear Mk. II during an interactive mission brief.
Roy Campbell - Hit campell with the metal gear Mk. II during an interactive mission brief.
Screaming Beauty - Defeat screaming beauty without killing her.
Young Snake - Start the eastern europe level.
Young Snake with bandana - Start the eastern europe level.