First use this one (Hit BACKSPACE and type):
!throw me a frickin bone here - Enable cheats
You may now hit backspace and type any of the other codes:

Code                         Effect 
------------------------------------
!captain scarlet           - God Mode 
!full monty                - God Mode Plus Items 
!stay frosty               - Give Sarge a ForceField 
!henry                     - Gives 30 Insecticide Spray 
!harsh language            - Gives 20 Fly Swatters 
!here's a lockpick...      - Give Unlimited Flame Napalm 
!mib                       - Give Sarge a Laser Rifle 
!this one goes to eleven   - Gives 3 Napalm Strikes 
!scotty                    - Give 3 SpaceMen Renforcements 
!hey stifler               - Give Unlimited Glue 
!one time...               - Give 3 Baseballs 
!spiny norman              - Give 3 HammerMines 
!let me down               - Drops Sarges Health to almost 0 
!pump me up                - Give Sarge a Steriods Boost 
!rate me                   - Show FPS 
!roody-pooh                - Give Unlimited Air Attacks 
!the meek                  - Lose Scenario 
!cut to the chase          - Win Scenario 
!halloween                 - Changes the Enemy Troops Into Zombies 
!time for bed              - Lose Scenario 
!mona lisa                 - Gives Random Item 
!florence                  - Gives Unlimited MediKit 
!johnny ricco              - Gives 3 Paratroopers 
!peep show Gives           - 3 Recons 
!heavenly glory            - Gives 3 AirStrikes 
!yippee!!!                 - Gives A Sniper Rifle 
!penny                     - Gives Unlimited M80's 
!hey dante                 - Unlimited Aerosol 
!the sun                   - Unlimited Magnifying Glass 
!whistle and flute         - Give Sarge a Flak-Jacket 
!i woke up this morning    - Gives 9 Blue Disguise 
!no sunblock               - Gives 9 Tan Disguise 
!incognito                 - Gives 9 Grey Disguise 
!i got two words for ya... - Gives A MineSweeper 
!haunt haunt haunt!        - Gives 10 Explosives 
!sprinkles                 - Gives 30 Mines 
!i like to keep this handy - Gives Unlimited Bazooka 
!patty melt                - Gives Unlimited FlameThrower 
!you want some             - Gives Unlimited Grenades 
!disco inferno             - Sets Sarge on fire (But Doesnt Hurt Him) 
!disco is dead             - Extinguishes Sarge's Fire 
!no one expects            - Summons a Horde Of Enemy Troops 
!italian job               - Sets Off A Huge Explosion Around Your Sarge 
!its dark                  - Hides All Enemy Troops on Mini-Map 
!door                      - Teleports Sarge to Cursor Location 
!only human                - Unknown Effect 
!sarge calibur             - Unknown Effect 
!know your role...         - Unknown Effect 
!hello neo                 - Unknown Effect 
!vic fontaine              - Unknown Effect 
!mojo                      - makes enemys move again 
!game over                 - Unknown Effect 
!when all else fails...    - Unknown Effect