Slag One was the designation for renegade Jedi Knight, Nathaniel Kenobi, during the Battle of Toola. This call sign designated the user as the leader of Slag Squadron. It would later be used by Nathan's grandson, Nathaniel Kenobi Solo during the Schism.
Following Nathaniel's departure from Novus Kamino Prime, Slag One was held by the best pilot and very few ever reached that position. It was considered to be one of the greatest honors ever to receive for a clone.