you cant! its available in ninja gaiden BLACK not sigma
not sure when you asked this question, but until now there are: -old arcade ninja gaiden games-not sure how they are called, -ninja gaiden (xbox) -ninja gaiden black(improved ninja gaiden for xbox) -ninja gaiden sigma Σ (more improved version for PS3) -ninja gaiden 2 (for xbox 360) and in the next months there will be a release of: -ninja gaiden 2 sigma Σ (another version for ninja gaiden 2, for PS3)!!
The third projectile weapon is an empty slot, it was removed from the game. It was the spear gun from Ninja Gaiden Black and Ninja Gaiden Sigma 1.
ninja gaiden black is more upgraded and with new enemies
for all the ninja gaiden games, there are NO cheats!!... I've done some cheats in the first Ninja Gaiden.
Ninja Gaiden Sigma was created in 2007.
Ninja Gaiden II happened in 2008.
Ninja Gaiden - arcade - happened in 1988.
Ninja Gaiden Shadow happened in 1991.
Ninja Gaiden Sigma happened in 2007.
Since Ninja Gaiden 2 was on the 360, almost definitely. Assuming Ninja Gaiden 3 is ever made.
Ninja Gaiden - arcade - was created in 1988-10.