Please note VGF's cheat codes have relocated to the main page.
HARD BOILED
Level 2 Boss Enable the level select and press and hold L1 while the game is loading. (Thanks to DANMONEY@webtv.net)
Level 5 Boss Enable the level select and press and hold R1 while the game is loading. (Thanks to DANMONEY@webtv.net)
Level Select After the opening credits, press and hold Up+X+Start and select Load Game. (Thanks to DANMONEY@webtv.net)