The Tactician's Drone also known as Sentry Drone is a flying drone similar to an ATAC and is the Tactician's secondary badge. You can throw a beacon that emits a green flashing light, and a friendly drone will come in. It fires bullets at enemies with surprising accuracy and power, capable of scoring head shots (which nearly always result in a one-hit kill), even on moving or far away targets. They seem to be as powerful (but much more accurate) than the Sentry bots, and like them can spot and kill disguised saboteurs and cloaked scouts.
Since the latest patch, sentry bots are less able to hit the drones with rockets. The drones also have a massive increase in armor, which makes it very difficult to defeat using conventional weaponry. The most effective method of destroying a drone is probably using an emplaced MG to fire a few shots into it, wait until it's finished its 'dodge' animation, and then fire at it when it has stopped moving (this will prevent the gun from overheating and, if timed right, will not give the drone a chance to fire back). Also the Drone is less likely to get a headshot on you due to the fact it aims for you using it's snout/sensor but the machine guns are emplaced on the sides of the snout/sensor, so it will merely hit you on your shoulders.