Gunmetal

Mission select:
Click Left Analog-stick, press Black, R, click Right Analog-stick, 
press White, L at the mission selection screen. 


Mission skip:
Click Left Analog-stick, press White(2), Back, click Right Analog-stick, 
press White during a mission. 


Alternate music:
Click Left Analog-stick(2), Right Analog-stick(2), press L, R at the 
title screen. 


Joke mission briefing:
Play missions 1, 3, 6, 8, 9 or 14, then press L(2), R(2), click 
Left Analog-stick, Right Analog-stick at the armory screen before launch.