Drone Weapons are extremely powerful missile weapons created by the Ancients. They are capable of guided flight and can be controlled from a control chair by someone with the Ancient Technology Activation Gene. Little is known about these weapons, but they have shown an ability to pierce Goa'uld shields and the hulls of Wraith hive ships.
City-ships such as Atlantis and Aurora class warship have thousands of these drones that can swarm and destroy ships. They were once used in defense of Earth during the Battle of Antarctica, easily penetrating the Goa'uld ha'taks. (SG1: "Lost City, Part 2")
After the Battle over Antartica, an outpost was created to study the Ancient outpost in Antartica. The scientists there studied an Ancient drone leftover after the battle. When doctor Carson Beckett was using the Ancient Control chair, he accidently activated the drone which chased after the incoming helicopter containing John Sheppard and Jack O'Neill. Beckett was able to stop the drone before it destroyed the helicopter. (SGA: "Rising, Part 1")