Immortality:
Gears Of War: Code (X-BOX 360) Free Download
During the game press: up, down, left, right, X, B, Y, A, up, down, left, right.
Endless ammo:
During the game press: up, down, up, down, left, left, A, B, X, Y, A.
Open all levels:
From the main menu press: up, down, left, right, A, B, X, Y.
Huge soldiers:
You must be the leader of the squad and during the game press: A, A, A, B, B, B, X, Y, X, A, up.