TechLookz

The Tower of Evermore:
To get to the Tower of Evermore, you'll need a bird type Innocent Devil with the long glide ability. 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.

Extra Features:
Sound Mode Beat Boss Rush with Hector. You'll find a music box lying around in the warp room. You can then you access sound mode from the title screen.
Boss Rush Mode Beat every boss in the game. Next time you go to a warp room, Boss Rush becomes a warp choice.
Crazy Mode Beat the game once. Start a new game with @CRAZY as a name to play on an extreme difficulty.
Trevor Mode Beat the game once. Start a new game with @TREVOR to play as Trevor Belmont.

Musical Chairs:
As you may of noticed, throughout the game there are various chairs you must sit in. If you happen to sit in them all, the room inside Cordova Town (the one that is pretty colorful with blue cloudy skies twirly around while little wierd rabbit/bug creatures are flying around with a target sign on their gut) will obtain a special chair in the center, though it really doesn't do anything for you, it's a nice little extra quest that you can do.

Optional Boss Pain:
In order to reach the optional bosses -- Legion and Nuculais -- you first must obtain the fifth Innocent Devil (Devil Type). With this, head back to Garibaldi Temple and slide under the crack in the wall back near the area with the four courtyards and Fencers. Proceed through the hallways, avoiding the Blood Bones and eventually you'll be in a hallway that is living. Save before you enter the boss area and make sure you're at least at level 50 or expect a tough fight.

XP Monopoly:
In the Forest of Jigramunt at the starting point head East. Once you have cleared the Vassago Lv.25 and two Sniper Orc Lv.24, the Spirit Lv.19 enemy will continually respawn in pairs. They drop a ton of Evo Crystals if you kill them with one blow. Use the Brooch item to give all the experience to your I.D. This is an easy way to see all of the forms of the I.D. and to level up the ones you'll use the most.