I don’t know if they officially count as grindhouse, but when I was a kid I loved a ton of the B-grade action movies that the Cannon Film Group put out in the 1980s. American Ninja, Delta Force, Cobra, Bloodsport, the Death Wish movies, Enter the Ninja, Revenge of the Ninja, etc. And, of course, the greatest ninja movie ever made:
Ninja III: The Domination.
This needs a line going up the Appalachians for the “You-uns” belt.