Unlock different difficulty settings  Finish the game once with either Chris or Jill.  You will have a choice of easy, medium and hard.

Unlock the alternate costumes  Successfully complete the game once and you will get a key.  Start your game and go to the room with the big mirror on the second floor of the mansion. Use the key to unlock the closet and the costumes will be there.  There are two alternate costumes for each character.  Every time you finish the game you unlock a different one. 

Get the Samurai Edge Gun  Complete the game with either Jill or Chris in under five hours.  Save your game at the end and once you start a new game you will have the Samurai Edge Gun.

Get the Grenade Launcher  Complete the game with either Jill or Chris in under five hours.  Save your game at the end and once you start a new game you will have the Grenade Launcher with Unlimited ammo. 

Real Survivor mode  Beat the game in the Once again mode in less than five hours.  This option blocks the ability to transfer items from one location to the other trough item boxes. 

Invisible zombies  Complete the game with either Jill or Chris twice.

Unlock producer commentaries and art Successfully complete the Invisible zombie mode under five hours. 

One Dangerous Zombie mode  Complete the game with both Jill and Chris.  A special zombie follows you around during the first part of the game and if you shoot him, the game ends.