Ninja Gaiden 2 Cheats

Five Of Yellow (15G): Beat the fifth Test of Valor
Four Of Green (15G): Beat the fourth Test of Valor
Indomitable Spirit (5G): Choose to continue the game 100 times.
Karma of the Master Ninja (20): Obtain all of the Crystal Skulls
Karma of the Mentor (20): Obtain 20 Crystal Skulls
Karma of the Warrior (20): Obtain 10 Crystal Skully
Kusari-gama Master (5): Complete the game using only the Kusari-gama
Lunar Staff Master (5): Complete the game using only the Lunar Staff
Mastered Counter Attack (5): Successfully performed the Counter Attack Technique
Mastered Flying Bird Flip (5): Successfully performed the Flying Bird Flip Technique
Mastered Flying Swallow (5): Successfully performed the Flying Swallow Technique
Mastered Furious Wind (5): Successfully performed the Furious Wind Technique
Mastered Invisible Path (5): Successfully performed the Invisible Path Technique
Mastered Obliteration Technique (5): Successfully performed the Obliteration Technique
Mastered Reverse Wind (5): Successfully performed the Revers Wind Technique
Mastered Shadowless Footsteps (5): Successfully performed the Shadowless Footsteps Technique
Mastered Ultimate Guidance (5): Successfully performed the Ultimate Guidance Technique
Mastered Ultimate Technique (5): Successfully performed the Ultimate Technique
Mastered Unrivaled Soaring (5): Successfully performed the Ultimate Soaring Technique
Nine Of Violet (15G): Beat the last Test of Valor
One of White (15): Purified the site of the the first Test of Valor.
Redeemed Genshin (15G): Defeat Genshin for the last time
Seven Of Red (15G): Beat the seventh Test of Valor
Silenced The Storm (15G): Defeat Volf for the second time
Six Of White (15G): Beat the sixth Test of Valor
Staunched The Blood (15G): Defeat Elizébet for the second time
The Art Of Inferno (5): Successfully performed the Art of the Inferno Ninpo
The Art of the Flame Phoenix (5): Successfully performed the Art of the Flame Phoenix Ninpo
The Art of the Piercing Void (5): Successfully performed the Art of the Piercing Void Ninpo
The Art of the Wind Blades (5): Successfully performed the Art of the Wind Blades Ninpo
Three Of Blue (15G): Beat the third Test of Valor
Tonfa Master (5): Complete the game using only the Tonfa
Two of Black (15): Purified the sit of the the second Test of Valor.
Vanquished Alexei (15): Defeat Alexei in battle
Vanquished Elizébet (15): Defeat Elizébet in battle
Vanquished Genshin (15): Defeat Genshin in battle
Vanquished Volf (15): Defeat Volf in battle
Vanquished Zedonius (15): Defeat Zedonius in battle
Vigoorian Flail Master (5): Complete the game using only the Vigoorian Flail
Way of the Acolyte (100): Complete the game on the Path of the Acolyte
Way of the Master Ninja (100): Complete the game on the Path of the Master Ninja
Way of the Mentor (100): Complete the game on the Path of the Mentor
Way of the Warrior (100): Complete the game on the Path of the Warrior

Mission Mode Achievements
Complete Mission mode with the following requirements to unlock the new Downloadable Content Achievements.

Acolyte of Missions (20): Complete all Karma Attack Missions on Path of the Acolyte
All Bronze (30): Obtain all Bronze Medallions in the Survival Missions
All Gold (30): Obtain all Gold Medallions in the Survival Missions
All Silver (30): Obtain all Silver Medallions in the Survival Missions
Eight Missions Completed (30): Complete 8 Missions
First Medallion (20): Obtain a Medallion in a Survival Mission
Four Missions Completed (30): Complete 4 Missions
Master Ninja of Missions (20): Complete all Karma Attack Missions on Path of the Master Ninja
Mentor of Missions (20): Complete all Karma Attack Missions on Path of the Mentor
Warrior of Missions (20): Complete all Karma Attack Missions on Path of the Warrior

New Game +
Save after completing the game to unlock New Game +. When playing a New Game + you will begin play on the same difficulty you completed with all weapons from the previous game at their current level. You will also keep your life, ninpo, items and essence.

New Game: Complete the game and save after Credit Scroll.

Unlockable Costumes
Complete the game on the specified difficulty to unlock these costumes:

Camoflauge Ninja Outfit: Complete the game on Warrior
Red Ninja Outfit: Complete the game on Acolyte

Hidden Silver Xbox
In the bottom of the Statue of Liberty across from the Test of Valor. You have to slice what it looks like to be bamboo curtain.

What it does in NGII is heal you, which you can do as many times as you like. It'll also make a sound from part of the 360's start up intro.

Yellow Essence Exploit (Chapter Six)
This exploit works during the sixth chapter, entitled The Lycanthropes’ Castle. After you fight the Giant Skeleton miniboss, you will be thrust into a battle with more Scorpion Skeletons. Fight them and wall run up to the next floor thereafter. Then, drop back down, fight them again, and repeat this process as much as you’d like for an infinite number of Yellow Essence.

Yellow Essence Exploit (Chapter Two)
Here's a great way to farm Yellow Essence during chapter two. After ridding the bridge you encounter of all of the archers and acquiring the Crystal Skull there, you will have to continue down another wooden path. This will lead to a pair of chasms that you have to swing over to get to the save point. Below that is a lower walkway full of enemies. Kill them all, and then scale a nearby ladder to reach the upper area again. When you go back down, the enemies will have respawned. You can kill them again to grab their Yellow Essence, climb back up, jump back down, repeating this ad infinitum to get all the Yellow Essence you want.

Yellow Essence Exploit (Chapter One)
The following yellow essence exploit can be completed on the game’s very first chapter, and is especially useful when playing on Master Ninja difficulty. Before and after crossing the bridge, you’ll deal with enemy ninjas (it’s the bridge where the first God of Life and a treasure chest can be found). After you cross the bridge, defeating ninjas as you go, head towards the middle alley that brings out two more ninjas on foot and another two ninja archers. Run back and charge up to Ultimate Level 2. Continue to run back and forth, and the ninjas will keep respawning and coming at you. If you have the skill, getting away with $40,000 while having 50%-75% of your health still available to you is a possibility.

Easter Egg: Prototype Xbox
About midway through Chapter 4, in the artifact room at the base of the Statue of Liberty, locate the nearby save point. Diagonally across from where the Save Point is, and directly to the right of the scroll on the podium, there is a false wall you can break apart. Inside, there will be a silver Xbox that regenerates Ryu's health.

Easter Egg: DOA4 Reference
In the game’s third chapter, you will be on the streets of New York. Near the beginning of the chapter, you will drop down into a sewer and fight there for a while. When you reemerge back on the streets from your brief sewer battle, an alley with a treasure chest at the end of it can be found. Right next to the chest is a building that says DOATEC in huge letters. DOATEC is the evil corporation that you do battle against in another Tecmo game, Dead or Alive 4.

Invincibility
Press up on the dpad and go to weapon select. Choose a different weapon but press a+b instead of just a. Now you will be invincible however you can only attack with the guillotine throw.