Zero Knuckle

The Zero Knuckle (ゼロナックル) is a weapon used exclusively by Zero in Mega Man Zero 4, which replaces both the Shield Boomerang and the rod weapons used in previous games. The Knuckle consists of a Z-shaped chip implanted into Zero's palms, represented by two Zs on his palms. These Z-chips allows Zero to punch enemies for low damage, but also to rip off certain types of weapons (such as blasters, rocket launchers or axes) from enemies to use them on his own. A successful theft of such a part normally results in the destruction of most enemies, but some enemies like Yadokroid and Lamplort X will lose a part of them first. The weapons or parts can have a number of uses, some of which have limited ammunition. If a stolen weapon is out of ammo or simply of no use any longer, it can be thrown away by pressing Select or in the pause menu, which can hurt an enemy as well. Since elemental chips have been omitted from the game, it's unknown if the Knuckle can use the chips like Zero's other weapons. It can also be charged, however the charged version of the Zero Knuckle is only a stronger punch. It is unknown whether this weapon was created by Cerveau or had been part of Zero all along, but artworks of Omega Zero from Mega Man ZX show him having a Knuckle on his own, but with an Omega symbol (Ω) instead of a Z though this is most likely used for the Rekkoha and Rakouhoha.

List of Zero Knuckle weapons
Zero can hold only one of those weapons by time.