Mark VIII tactical missiles are a type of weapon used by the Tau'ri that are standard aboard Daedalus-class warships.
Colonel Caldwell had the Daedalus launch several Mark VIII tactical warheads at a Wraith Hive Ship. However, they were intercepted by Wraith Darts long before they reached the enemy ship. If beamed aboard Hive-Ships, they cause considerable damage resulting in its destruction. They also cause considerable damage when they impact a ship's hull, however several are required to completely destroy one. (SGA: "The Siege, Part 3", "No Man's Land")