Hidden And Dangerous cheats and cheat codes for Dreamcast

Unlock all missions and additonal options:
Go to the name entry screen and type the following codes as your name: "RVL"
Keep the "L" highlighted the last letter, so your name will appear as 
"RVLL" with the second "L" still flashing. Push Start to delete your 
name and press B to go back to the main screen. While playing pause 
the gameplay to bring up a cheat menu.

Cheat Codes:
Type "IWILLCHEAT" as a name or at any menu screen during the start of the game
on a Dreamcast Keyboard to enable cheat mode. Then, enter one of the following
codes to activate the corresponding cheat function:

Pause the gameplay and type the following cheat codes on your Dreamcast keyboard.

All items: Type "ALLLOOT"
Big head mode: Type "FUNNYHEAD"
Display player's coordinates: Type "PLAYERCOORDS"
Enemy behind view: Type "ENEMYB"
Frontal view of enemy: Type "ENEMYF"
German version: Type "BLUESTARS"
Invincibility: Type "CANTDIE"
Kill everybody including hostages: Type "KILLTHEMALL"
Mission failure: Type "GAMEFAIL"
Mission skip: Type "MISSIONOVER"
Open all doors in current mission: Type "OPENALLDOOR"
Restore all team members health: Type "GOODHEALTH"
Revive dead teammates: Type "RESURRECTION"
View ending sequence: Type "SHOWTHEEND"
Wireframe graphics: Type "DEBUGDRAWWIRE"