To unlock cheats, look for small, glowing, white orbs (eggs) hidden throughout Transylvania. Stand on one and press Circle. A message should appear at the bottom of the screen with more information about what was unlocked.
Successfully complete the game under the hard difficulty setting.
In mission two, get past the train station area and look behind the 'dragon' door.
To get the Rifle, win all of the Easter Egg mini-games twice.
When battling Dracula for the first time in Castle Frankenstein, a bunch of lab equipment will be near Velken off to the side.Look for a batch of green ooz, jump in and click the action button until you find it. You may only keep it if you get it before killing Dracula otherwise you must go back for it.
Alternate Gatling Gun
When starting out on Mission 12, you will notice a bunch of staircase platforms. Then wraiths will swarm at you from every corner. Slay all the wraiths and make your way to the middle stair platform to the barred door to your left. Charge up the Alternate Lightning Gun and juice the power stone in the wall. Walk inside and recover the Alternate Gatling Gun. If you don't have the Rifle, this will do for BIG DAMAGE.
Alternate Lightning Gun
When escaping Castle Frankenstein on level 8, you will pass through familiar rooms. When you get to the room where you first encountered pygmy bats, jump through the hole in the wall in which you came through to get up there. As you jump down, you will notice a pool of spilled goo off to the side from one of the containers. If you look closely, a glowing lightning gun will be lying in it. Add it to your growing collection of superb weaponry.
When you get to the part where you have to fight the three Vampires, take out the one on the left first. When the center Vampire is going to attack, she will make a screeching type of sound. When she does that, get ready to dodge her attack. When she uses her lightning attack, hide behind the pillar. When you take out the Vampire on the left, the center Vampire will transform. The transformed Vampire will land on the ground and remains still. Back away and do not get hit when she dives after you. If you follow this and attack at the correct times, you should be able to defeat them.
In mission two, look behind the 'dragon' door at the start of the train station to find the cheat icon. Use the alternate Tojo blades to collect it.
Just after entering the side courtyard of Castle Frankenstein, turn left (in the direction of the tower). Double jump around until you can see the cheat icon. Use the grappling hook to reach it.
Mission One Cheat Icon
When you first can use the grapple, you will see something white glowing. It is the cheat icon. After using your grapple, jump and get it.
Once you have completed the game and wait for the credits to roll, you will be prompted to save your game on a new game option. Do so and you can start the game with all previously unlocked cheats, power-ups, and items.
In mission two, look near the Ghost Body cheat icon to find the Big Head cheat icon near a wagon.
When a Boss or other strong enemy grabs you, keep pressing L1 (Shoot) to take away great amounts of life away from them.
Find the large gear room in the Castle Frankenstein's basement. Stand on the wooden platform on the right side of the room, then use the grappling hook to reach it. Alternately jump on the stallions while fighting Demon Verona on the stagecoach. Get knocked off the stallions by of the brides. An intermission that shows Van Helsing getting dragged under the coach will appear. Repeatedly tap Circle while under the coach to collect the cheat icon. Alternately, first complete the game and get the Gatlin Gun upgrade. When you get into the gear room, instead of going into the door, power it up and go to the other side. Use your grappling hook and it will take you to a stone door. Use your Gatlin Gun upgrade to start a intermission sequence and it will be Armory Anytime.
Complete mission five, then get egg in the well. Defeat the werewolf in the town, and put the egg on a pedestal to get the cheat icon.
Successfully complete the game wearing your hat on every mission.
In mission six, enter the side entrance to the castle. After defeating the werewolves, walk to the lion gargoyle that is pouring water and press Circle. The cheat icon is in its mouth.