Infinite Ammo Sub Machine Gun location
After exiting out of the bathroom window (after the start of the game) go left; it is at the dead end.
Beginner fighting difficulty setting
Intentionally die twice during game play under the normal fighting difficulty setting.
Life display option
Finish the game using hard difficulty to unlock Life Display at the extra options screen.
Possessed ending
Kill all the monsters with any weapon except melee ones.
Death scenes
There are areas in the game where special death scenes occur for your character if you figure out how to trigger them.
Heather Beam
Kill 333 enemies. Playing through the game several times will achieve this.
Life bar
Finish the game under the hard action and hard riddle difficulty settings to unlock the Life Bar option at the extra options screen.
Weapon locations
You can find a shotgun in the subway and a machine gun in the hospital.
Claudia necklace
When the intermission sequence between Claudia and Vincent is finished and Vincent dies, use the necklace on Claudia.
Order of tarot cards at the last door of the game
Normal difficulty:
Northwest position: Eye Of The Night
Northeast position: Moon
West position: High Priestess
East position: Fool
South position: Hanged Man
Hard difficult
Northwest position: The High Priestess
North position: The Eye Of The Night
Center position: The Fool
East position: The Moon
Southwest position: The Hanged Man
Beam Saber location
At the end of the hallway where you get the bookstore key; hanging on the door.