The super rig is a Gnomish invention that Nogg in Orgrimmar wants the blueprints for. According to him it is "better than all our shredder models combined". It is unknown if by "our" he means all goblins or just those in service to the Horde.
It is never actually revealed specifically what this rig is used for, but because it is compared to goblin shredders it can be assumed that this is some sort of pilotable mech, possibly the type that Sicco Thermaplugg and Mekgineer Steamrigger are using.
It might be possible that the super rig is the Super Reaper 6000. However, its unlikely to be the case, as the blueprints (for the super rig) are stated to exist within Gnomeregan, and plans for the Super Reaper are held by operators in the Stonetalon Mountains.