In the 1966 Toei fantasy flick The Magic Serpent, the hero Ikazuchi-Maru is ambushed by a gang of boomerang-wielding ninjas (who are way more dangerous than hula-hoop-wielding ninjas).

The dastards succeed in decapitating our hero, but he's got one last stupid ninjutsu up his sleeve. Also, witness the most ignominious death of a ninja henchman ever committed to celluloid.

This clip comes courtesy of Sardonicus1313's YouTube channel, which is chock full o' ninjutsu and kung fu weirdness, namely "The Vagina Bubble From Hell."