The arcade Teenage Mutant Ninja Turtles games (and their home-system ports) are all about sending swarms of enemies at you that you have to defeat with your Ninja Cunning(tm), along with whatever pointy weapons you can find.

In the fourth home-system Turtles game (which is the second arcade game, try not to think about that too much) you get a couple of new moves to help you squash the hundreds of robots that stand between you and the end of the game, one of which is the 'Grab the arm of an enemy and slam it on the ground repeatedly' maneuver.

To do it, you first hit the Foot Soldier with your weapon to double it over, and then hold Down and press the attack button.

Done right, you'll grab the unsuspecting Soldier's arm and start slamming away, back and forth, until it runs out of health.

But! This maneuver has two properties that make it extra useful:

1. Any enemies that you hit with your new club are instantly dispatched, regardless of the amount of health they have and

2. While you're doing it, you're completely invulnerable to attacks

Combine those two things and you have a seriously effective method of clearing out a group of enemies

Which, as you progress through the game, you're going to need.