Tactical drone

From Memory Alpha, the free Star Trek reference.

A tactical drone is a type of drone in the Borg Collective.

Members of Species 4228 make excellent tactical drones. (VOY: "Think Tank") Members of Species 6961 have also been observed as having been assimilated into tactical drones. (VOY: "The Raven")

Tactical drones have been noted to possess a tritanium infrastructure. (VOY: "Dark Frontier")

It is unclear exactly what function tactical drones serve in the Collective. It is possible that they are drones which perform various functions concerning battle planning.

Another possibility, based on the reference to a tritanium infrastructure, is that they are hardened versions of standard drones designed to better withstand physical combat or other potentially dangerous conditions.