Castlevania Lament of Innocence

All Skills Mode:
Clear the game with Leon once and save that game. Start a new game on another slot and enter the name @LLSKILL.
Leon will have all his skills when he begins the game. 

Unlock Boss Rush Mode:
Clear the game with any character and save that game. That game's character may head back to the stage select room and opt to try Boss Rush Mode, that is a time attack mode against all the bosses in the game in the order they appear in the Encyclopedia.

Unlock Crazy Mode:
Clear the game with Leon once and save that game. Start a new game on another slot and enter the name @CRAZY.
Crazy mode is much harder than the normal game. 

Unlock Jade Mask Item:
Clearing the game will unlock the Jade Mask for sale at the shop. 

Unlock Joachim's Game:
Clear the game with Leon once and save that game. Start a new game on another slot and enter the name @JOACHIM.
Joachim's game is played differently, and the character has no access to any weapons, armour, or health restoration items. 

Unlock Mobius Brooch Item:
Clearing the game on Crazy Mode will unlock the Mobius Brooch in the shop. 

Unlock Pumpkin Game:
Clear the game with Joachim once and save that game. Start a new game on another slot and enter the name @PUMPKIN.
The Pumpkin game starts the character off with all skills and the Vampire Killer, as well as increased stats. However, there are no subweapons available other than the initial subweapon. 

Unlock Sound Test:
Clear the game once with any character and save that game. The Music Box will be available for purchase in Rinaldo's shop for all future games (you only need to buy it once and save the purchase to that game).

Castlevania: Curse of Darkness Cheats

The Tower of Evermore:
To get to the Tower of Evermore, you'll need a bird type Innocent Devil. From the top of the Tower of Eternity, face the moon in the background so that it is directly in front of you and jump off the ledge, gliding all the way to the Tower of Evermore.

The monsters here are much harder than the ones found in the Tower of Eternity.

Boss Rush Mode.:

Enter a warp room after beating the game.

Moai Statue.:
Have a Lament of Innocence save file on your Memory Card.

Sound Mode:
After beating Boss Rush Mode, the music box should appear in the warp room. With this item, you should be able to access the Sound Mode Option to play various music from the game.

Moebius Brooch:
Once you beat Crazy Mode, the Moebius Brooch will be available in the shop. Equipping this item allows you to do special moves without using hearts.

Trevor Mode:
After beating the game once, if you start a new game and put @TREVOR as your name, you'll start the game as Trevor Belmont.

Crazy Mode:
After beating the game once, if you start a new game and put @CRAZY as your name, you will start the game at a higher difficulty setting.

Castlevania: Circle Of The Moon

Magician mode: 
Enter FIREBALL as a name and start a new game. The word "Magician" will appear on the option screen to confirm correct code entry. All trading cards will be available under the DSS option.

Shooter mode: 
Enter CROSSBOW as a name and start a new game. The word "Shooter" will appear on the option screen to confirm correct code entry. Nathan will have a substantial number of hearts, extra sub-weapon damage, and can use the Homing Dagger sub-weapon in this mode.

Fighter mode: 
Enter GRADIUS as a name and start a new game. The word "Fighter" will appear on the option screen to confirm correct code entry. Nathan will be stronger and able to sustain more damage. There are no trading cards in this mode.

Thief mode: 
Enter DAGGER as a name to get your character thief stats.

Spinning attack: 
When using the whip, hold down Attack to make it spin around in a circle. It will act like a shield, so you cannot get hit by small enemies around you. Note: You cannot move while doing this attack.

Defeating Dragon Zombies (Twin Dragons): 
To defeat the Dragon Zombies easily, whenever you get hurt, jump up to the platform by the door where you entered the room and activate the Jupiter + Mandragora DSS combo to heal yourself. A fireball may hit you every once in a while, but it is very rare.

Defeating Death: 
To defeat Death very easily, just activate the Jupiter + Manticore DSS combo. His sickles cannot hit you, and by this point in the game you will probably never run out of MP because this combo will use it slower than you restore it.

Enemies that drop DSS cards: 
The following is a list of enemies and locations that drop various DSS cards.

Action Cards:

Mercury: Bone Head in Catacomb.
Venus: Slime in Catacomb, Abyss Corridor (hidden room), and Audience Room.
Jupiter: Heat Shade in Machine Tower.
Mars: Bloody Sword in Chapel Tower.
Diana: Man Eater in Underground Gallery.
Apollo: Arch Demon in Underground Storage.
Neptune: Ice Armor in Underground Waterway.
Saturn: Fallen Angel near the Battle Arena.
Uranus: Scary Candle in Golem Boss Room (defeat Camilla first).
Pluto: Trick Candle in Cerebus Boss Room (defeat Camilla first).

Attribute Cards:

Salamander: Bomb skeleton in Catacomb.
Serpent: Earth Demon in Catacomb.
Mandragoras: Axe Armor in Abyss Corridor(in a hidden room), Audience Room.
Golem: Electric Skeleton in Audience Room.
Cockarice: Stone Armor in Machine Tower.
Manticore: Thunder Demon in Machine Tower.
Griffon: Skeleton Athletes in Audience Room (hidden room way to the right).
Thunderbird: Were-Panther in Chapel Tower.
Unicorn: White Armor in Battle Arena.
Black Dog: Devil Armor in Battle Arena.