To use these cheats you first have to press \ or BACKSPACE to enter message mode, then type !when all else fails... to enable cheat mode. You can then enter one of these cheats

Vulcan gun
!a better tomorrow

Mines
!acme discs

Armageddon
!armageddon

Sniper rifle
!beautiful nikita

End of Phoenix, etc.
!cliche ending

Healing
!doctor doctor

M-80
!fourth of july

Air strike
!geronimo!

Explosives
!gnomish inventions

Sniper rifle
!god of gamblers

Lose mission
!i give up

Grenades
!i have a rock

Flight mode
!jumpjets

Stealth mode
!ninja arts

No rocket launcher
!no rocket launcher

Paratroopers
!paper dolls

Flaming Sarge
!phoenix!

Mine sweeper
!pooper scooper

Aerosol spray
!roach spray

Medical kit
!rubber cement

Magnifying glass
!ruby ray

Invincibility
!santini

Disguise
!shrink wrap

Disguise
!smorfs

Full map
!spidey senses tingling

Commit suicide
!suicide kings

Overwhelmed by enemies
!surprise party

New background sound
!techno

Restart mission
!veni vidi vinci

Flame thrower
!village people

Reconnaissance flights
!watchtower in the sky

Unknown
!patton's speach

Unknown
!fond memories

Turns Tan army to Zombies
!night of the walking dead

Unknown
!aluminum foil

Gray Disguise
!metal sheeting

"Go Bruins" message
!ucla

Unknown
!moleman

Unknown
!warp 6

Give all guns and cars
!COOKIE JAR

Level Skip and 8 Men
!MEN SKIP