The House of the Dead 2 & 3 Return Cheats

Go through original mode, but at the begining select the 2.0 bullets and Double score items. Play through original mode, rescuing all civillians except for the one on level 4 (the guy the Zombie is holding on to). Then beat the game. You'll end up in a Secret room. In the trunk is a Rogan Costume and an Infinite Credits icon.

To access one of the bonus rooms at the end of the game, you must get there without killing any hostages, or allowing any hostages to be killed.

Shoot a cat and it will lead you to a bonus item.