Beat the game and then use @TREVOR as your profile name.
Beat the game and then use @CRAZY as your profile name.
Beat the game on Crazy difficulty and this item will be unlocked in the shop.
Boss Rush Mode
Finish the game and defeat all of the the optional bosses. Boss Rush Mode will then be unlocked in the warp rooms.
Complete Boss Rush Mode and then head to a warp room. You'll find a music box, which will let you check out the sound test.
This one will refill your health when you use it, and it's worth a few thousand gold. If you have a Lament of Innocence save game on your memory card, the Moai Stone can be found outside of the gates of the Abandoned Castle.