7. Type 03 Ship
In the Next Generation episode Descent, the Enterprise-D encountered the brother of Data, the Soong-type android Lore. Since seeing him last, Lore met up with the liberated Borg Hugh and a number of other drones who were separated from the Collective after being linked with Hugh.
Lore and the Borg somehow came into possession of an extremely strange ship, apparently Borg in design, that a display on the Enterprise labeled as "Borg Type 03," likely because it was the third class of Borg starships identified by Starfleet (after Cubes and Scout Ships). The design of this class is so strange, asymmetrical, and dissimilar to other Borg vessels that Picard speculated it may be an assimilated ship from another species. We unfortunately never learned the true origin of this mysterious craft, and other Type 03 ships were never seen.
Regardless of its true origin, the Type 03 craft from Descent was equipped with Borg technology including advanced shields, weapons, and the ability to travel through transwarp conduits. The Enterprise-D was at a huge disadvantage, and was only able to destroy the vessel thanks to some quick thinking by Ensign Taitt, who suggested using a particle beam on a star to engulf the Borg ship in a solar eruption.