Trial mode: [Submitted by:Jason Squires]
Quickly press Up, Down, Down, Right, Right, Right, Left, Left, Left, Left at the title screen. Hold Triangle and press Start to get trial mode. A gunshot confirms the correct code entry.

Sudden death mode: [Submitted by:Jason Squires]
Quickly press L2, R2, L2, R2, Circle, Triangle, Circle, Triangle at the title screenh. Hold L1 and press Start to get sudden death mode. A gunshot confirms the correct code entry.

Maximum power mode: [Submitted by:Jason Squires]
Quickly press L1, R2, L2, R2, L2, Triangle, Circle, Triangle, Circle at the title screen. Hold L1 and press Start to get maximum power mode. A gunshot confirms the correct code entry.

Multi-player characters: [Submitted by:Jason Squires]
Quickly press Up, Down, Down, Right, Right, Right, Left, Left, Left, Left at the title screen. Hold Circle and press Start to get all Bosses, engineers and a few army characters in multi-player mode. A gunshot confirms the correct code entry.

Multi-player characters alternative: [Submitted by:Jason Squires]
Complete the game on easy and normal difficulty.

Maximum power, sudden death and trial modes: [Submitted by:Jason Squires]
Successfully complete the game on hard difficulty.