Invincibility

Press: A, A, A, A, Y, X, B, A, Up, Up, Down, Right, Left. If you enter the code correctly, you should here a beep.

Achievements

Complete the following achievements to unlock the indicated number of Xbox Live Gamerscore points.

Scout Complete (20 points): Complete the Scout arc in Story mode.
Soldier Complete (20 points): Complete the Soldier arc in Story mode.
Sniper Complete (20 points): Complete the Sniper arc in Story mode.
Gunner Complete (20 points): Complete the H. Gunner arc in Story mode.
Defense Complete (20 points): Complete the Defender arc in Story mode.
Command Complete (20 points): Complete the Commander arc in Story mode.
All Tact. Complete (20 points): Complete all missions in Story mode.
Tact. Instructor (20 points): Earn top marks in every Story mode mission.
Hover Specialist (20 points): Deploy the Hover Chassis 50 times.
Wheel Specialist (20 points): Deploy the Wheeled Chassis 50 times.
Biped Specialist (20 points): Deploy the Bipedal Chassis 50 times.
Inverse Specialist (20 points): Deploy on Inverse Chassis 50 times.
Tread Spec. (20 points): Deploy on Treaded Chassis 50 times. 
Multi Spec. (20 points): Deploy on Multi Chassis 50 times.
Crushing Award (20 points): Wipe out the enemy and live 100 times.
Storming Award (20 points): Attack the opponent first 30 times.
Survival Award (20 points): Return alive 10 or more times in a row.
Red Flag (20 points): Win a total of 100 times or more.
Bronze Wing (20 points): Destroy 50 or more enemy HOUNDs.
Bronze Flag (20 points): Secure a COMBASs total of 100 times.
Bronze Hammer (20 points): Destroy the enemy HQ and win 50 times.
Silver Wing (20 points): Destroy a total of 100 enemy HOUNDs.
Silver Flag (20 points): Secure COMBASs a total of 300 times.
Silver Hammer (20 points): Destroy the enemy HQ and win 100 times.
Scout Valor (20 points): Scout experience level maxed.
Soldier Valor (20 points): Soldier experience level maxed.
Sniper Valor (20 points): Sniper experience level maxed.
Command Valor (20 points): Commander experience level maxed.
Gunner Valor (20 points): H. Gunner experience level maxed.
Defense Valor (20 points): Defender experience level maxed.
Bronze Patriot (20 points): Stay with the same nation for 3 seasons.
Gold Eagle (20 points): First in total fame for a given period.
Gold Cross (20 points): First in seasonal fame at end.
Gold Wing (20 points): First in average total fame for a given period.
Gold Hexagon (20 points): First in average seasonal fame at end.
Gold Sword Cross (20 points): First in total conquest points for period.
Gold Lion (20 points): first in seasonal conquest points at end.
Marching Service (20 points): Travel a total of 1000000.
Military Service (20 points): Deploy total of at least 300 times.
Capital Occupation (20 points): Affiliated nation destroys another.
Nation Resurrector (20 points): Successfully revive affiliated nation.
Neroimus War Medal (40 points): Affiliated nation wins Neroimus War.

Additionally, there are seven secret achievements, four of which remain unknown.

Humane Award (20 points): End five times in a row without killing the enemy.
Bloodless Award (20 points): Win five times without attacking the enemy.
Silver Patriot (20 points): Donate to affiliate nation once.