Headhunter: Redemption (PlayStation 2)
Applying the below code will enable an elaborate debug menu. This unlocks a level select menu in the main menu, and will enable the debug menu when holding Select button while in-game. The options here are fairly self-explanatory. This will also put a build date in the top right corner of the screen.
USA codes: Master Code (only needed for cheat devices) 90423B20 0C108E70 Enable Debug Mode 0043B8C8 00000001
The second part of the debug menu can be activated by holding Select and pressing D-Pad Down. One of the interesting options here is the ability to use save states. It isn't clear if taking screenshots work.
The debug mode code will also enable a level select menu in the main menu.