Decapping Die
Also: Depriming Die
A reloading die whose only job is to punch the spent primer out, separate from any case sizing, so brass can be cleaned before it touches a sizing die.
A standalone decapping die holds a single pin that pushes the fired primer out through the flash hole, and nothing else. It does no resizing, so a handloader can decap dirty brass first, then wet or ultrasonic clean the cases and primer pockets before they ever touch a sizing die.
Keeping the steps separate protects the more expensive sizing die from the carbon and grit baked around a fired primer, and it lets the pockets be cleaned while they are open. It runs in any standard reloading press.