Castlevania II: Belmont's Revenge

Castlevania II: Belmont's Revenge is the much more Castlevania-like sequel to Castlevania: The Adventure on Game Boy.

Weapons
While both regions of the game share the Holy Water, the other weapon is different in each. The Japanese version offers a boomerang, but the US version has the axe, either because it was more useful or less broken.

Sound test
Use the password (Heart)-(Heart)-(Heart)-(Heart) to bring up the game's sound test.

Also, enter Gameshark code and scroll down past 'DEMO 2/FAITH' to find the inaccessible entry SELECT BGM/NEW CHURCH, the theme that plays at the stage select screen.

Sound test titles
As seen above, the track titles were changed to generic names in the overseas releases, likely done to remove their religious references.