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.