Transphasic torpedo

Only seen in the Voyager episode "Endgame", the Transphasic Torpedo is apparently able to pass through enemy shields and perhaps even phase through the hull of enemy ships. These weapons remain an almost complete mystery, except for the obvious fact that they do a very good job of destroying Borg Cubes. These cubes can be relatively easily destroyed through attacks to 'weak points', so this is the most conservative explanation for their effects.