Ancillary weapon

Weapon used for a secondary or auxiliary purpose

An ancillary weapon is a weapon used to supplement a primary or main weapon in the event it cannot be used or is ineffective in a certain application or situation. Examples of ancillary weapons to main weapons include a melee weapon to a ranged weapon, a sidearm to a service weapon, or a light gun to a heavy cannon.

This keyword could refer to multiple things. Here are some suggestions: