Castlevania: Dawn Of Sorrow [NDS]

Completion bonuses
Successfully complete the game with the best ending to unlock Boss Rush mode, Sound Test mode, and New Game +. Successfully complete the game with Soma on the hard difficulty setting to get the Hell Flame Soul (triple fireball) move.

Julius mode
Equip the Paranoia soul and without Mina's charm equipped, enter the mirror to fight Dario's inner demon.

Play as Alucard in Boss Rush mode
Successfully complete the game with Soma with a 100% completion and complete Julius mode. Then at the Konami logo, press Up(2), Down(2), Left, Right, Left, Right, B, A. Remain idle until the Konami logo appears again, then press Up, Down, then hold Up until the sound of a door opening is heard. Select Boss Rush mode to play as Alucard with his Alucard Set.

Attack faster
If you have a heavy weapon like a great sword, slow attacks can be a problem. To hit an enemy twice quickly, stand very close to them and attack. Then just as it connects, press L to dash backwards. As soon as it stops, you can attack again; if you are still close enough it should hit. This is quicker than just attacking twice normally.

Chaos Ring
Get 100% of the Souls to get the Chaos Ring, in the abyss.

Death Robe
Finish Boss Rush mode in less than six minutes to get the "Death Robe". It a powerful armor, but Dracula's Tunic is better.

Easier Boss Rush mode
Activate the Devil Soul and use the Valmanway Sword. You can take down all the Bosses in less than five minutes.

Nunchakus
Finish Boss Rush mode in less than seven minutes to get the "Nunchakus" weapon.

Play as Alucard in Boss Rush mode
Successfully complete the game with Soma with a 100% completion and complete Julius mode. Then at the Konami logo, press Up(2), Down(2), Left, Right, Left, Right, B, A. Remain idle until the Konami logo appears again, then press Up, Down, then hold Up until the sound of a door opening is heard. Select Boss Rush mode to play as Alucard with his Alucard Set.

Rare Ring
Have the Game Boy Advance game Castlevania: Aria Of Sorrow in the cartridge slot and start a new game to have the Rare Ring in your inventory.

Rocket Launcher
Finish Boss Rush mode in less than five minutes to get the Rocket Launcher "RPG".

Terror Bear
Finish Boss Rush mode in less than eight minutes to get the "Terror Bear" weapon.