Fighting Force 2 [PSX]

Cheat mode:
Hold L1 + L2 + R1 + Triangle + X + Left when "Press Start" appears at the opening screen. Select the "Start Game" option and choose a level. Your character will have unlimited ammunition and will be invincible during game play. Note: The game cannot be saved when cheat mode is enabled.

More rage:
Hit a vending machine until the pop cans fall out. Stand over a can and press X to increase your rage meter.

Defeating the steel worker:
When facing the steel worker at end of level 1, do not let him hit you. Hit him a dozen times and he should fall down and disappear.

Completing level 2:
When you get to the end of level 2, get the shotgun and shoot one man two times. Then, send a grenade or two flying his way to finish him off. For the other three men, put as many shells as you can in them.

Invincibility and Infinite Ammo
At the title screen, press the following:
L1+L2+R1+X+Triangle+Left

Level Select
At the main title screen, press the following:

L2+R2+Square+Circle+Up

Start a new game, and you'll be taken to a Level Select Option, highlight a level and press X.