The X-Files: Resist or Serve/Codes

At the title screen, enter one of the following button combinations:
 * One-hit kills: psx: Cpsx: L2psx: Down Dpadpsx: R1psx: X
 * Infinite ammo: psx: L1psx: L2psx: Xpsx: R2psx: R1
 * Unlock all bonus features: psx: Left Dpadpsx: R1psx: L1psx: Down Dpadpsx: C
 * Unlock all levels: psx: R2psx: Right Dpadpsx: L2psx: Up Dpadpsx: S
 * Invincibility: psx: Up Dpadpsx: Spsx: Cpsx: Xpsx: Down Dpad
 * Explosive bullets: psx: Xpsx: Cpsx: Spsx: L2psx: R1