I like American Ninja III because the Ninja overwhelms so many of the tin-plated goons this society has to offer -- single handedly!. That is what makes this movie my favorite, and I've never seen another quite like it. I'd like to know if there are any others with the same combatants!
"Piranha Part Two: The Spawning" has mutated Piranhas attacking a tourist beach resort. They are some mutated fish that the US government developed to dump into the rivers in Vietnam and eat some Cong. There aren't any ninjas, or v8 even, but there are Piranhas that can fly and survive out of the water and bite you in the face.
There's a couple of little known Mats Helge movies that's really silly... allthough not at all like Ninja III though.
Ninja Mission CIA, KGB and hired Ninjas battle it out over some weird formula that has been encrypted to look like a romance-novel, only the scientist who invented it and his scantily clad daughter knows how to decrypt it.
Russian Ninja ( also called Russian Terminator) Beyond description really...
Oh, and not to forget:
9 Deaths of the Ninja Looks and sounds like a spoof-film that's been pulled out of postproduction too soon.
And over at Badmovies.org I have heard of the flick Cyber Ninjas... I haven't seen it... but it's description makes me want to get it as soon as possible... "Namco made a movie. It has lasers, samurai swords, and very little coherence."
Machine Girl contains its fair share of Crazy Yakuza Ninjas....
Oh, And I'll end this all with a link to the end fight of Godfrey Ho's Black Ninja (aka Ninja Silent Assassin):
First of all, HOLY CRAP THIS POST IS FROM 20 YEARS AGO!!
Back on topic
Big Trouble in Little China
The Last Dragon
Also, I think the OP posted in the wrong forum and meant to post under AMERICAN NINJA 3, and not NINJA III. But oh well hopefully in the 20 years since posting they've figured it out.