Press ~ while playing to display the console window. Use one of the following codes:

Effect - Code

All U.S. missions unlocked - cheat.openus
All Vietcong missions unlocked - cheat.openvc
Full health - cheat.heal
Mission skip - cheat.nextmission
Toggle crazy gun mode - cheat.erikgun
Toggle God-mode - cheat.god
Toggle unlimited saves - cheat.saveunltd