Go to "Players", and then "Cheats". Activate the following cheats by entering the corresponding codes:

CHEAT FUNCTION - CHEAT CODE
Programmer message - iopred
Programmer message - DayDream
All weapons - up up down down left right left right b a select start
Bow and arrow - John Rambo
Chain gun - Old Faithful
Sniper rifle - Its a Jackal
Double shotgun - This is my boomstick
Flak Cannon - Shrapnel
Guided launcher - Follow the leader
Drunken launcher - Moonshine
Goo gun - Gloop
Spark Plug - 9 Volt
Bladerang - Australians all let us rejoice
Laser rifle - Alpha
Auto laser rifle - Beta
Laser shotgun - Gamma
Anytime - I dont have time to bleed
Airstrike - Call in artillery
Level select - You are the moon master
A-Bomb Launcher - Missile launch detected
Soundwaave - Bass in your face
Black Hole Generator - Wash away the rain
Amazon Jungle - Ive got jungle fever, shes got jungle fever
Canyon Lands - Aint no mountain high enough
Zones 4 and 5 - Who rides the wrecking ball