Zero Buster

General description
The Z-Buster is Zero's weapon in Mega Man X, Mega Man X2, and Mega Man X3. He actually gains the Z-Saber in Mega Man X2, although the Z-Buster remains his primary weapon until Mega Man X4. Also, note that the Z-Buster seems to be much more powerful that X's X-Buster, as it sufficiently damaged Vile's ride armor (even though it was only half charged) while the X-Buster could not even visibly scratch it (this was perhaps due to X not being at full strength at the time as this was mentioned by Zero himself). However, in Mega Man X5 and X6, the Z-Buster is less powerful than X's, being unable to charge shots, and only fires a slow and weak shot (though it is more stronger in X6, but not by much).

In the Mega Man Zero series the Z-Buster is lost, replaced by the Buster Shot Gun, which Zero took from the dead Milan to protect Ciel. The Buster Shot Gun cannot charge by itself, but artworks show the deactivated Z-Saber slotted in the gun and allowed charging through the Z-Saber's own technology.