Finish the game, then start a new game and enter any of the passwords below.
Advanced Intelligence: Enter the password X-X!V"Q and start the game. Your intelligence will be boosted, but your strength will be weak.
Play as Richter: Enter the password RICHTER and start the game. You can now play as Richter Belmont.
Axe Lord Armor: Enter the password AXEARMOR and start the game. You'll find a cool new suit of armor in your inventory.
Secret Passage
At the outer-wall section of the castle, defeat the Armor lord and go into the next room. Slash the far left wall, get the Meat, and stand in the hole you've created for 20 seconds. An elevator will take you into a secret room containing Jewel Knuckles and a Mirror Cuirass.