First, beat the game to make these work. During gameplay, pause, hold both trigger buttons (L and R), and then press the following:

Invulnerability - BLUE, RED, BLUE, UP
Restore Health - BLUE, BLUE, RED, RED
All Upgrades - UP, DOWN, YELLOW, BLUE
Infinite Missles - BLUE, BLUE, DOWN, RED
Perfect Mode - RED, DOWN, YELLOW, GREEN
Always Devastating - YELLOW, UP, YELLOW, DOWN
Targeting Indicator Mode - DOWN, RED, UP, BLUE
Unlock Four-Hit Combo For Aragorn - UP, BLUE, YELLOW, DOWN
Share XP (co-op) - RED, GREEN, GREEN, GREEN
Share health (co-op) - YELLOW, UP, GREEN, GREEN
Unlimited respawns (co-op) - RED, BLUE, UP, RED
All interviews - GREEN, BLUE, GREEN, UP