Cool idea. My list is based on engineering and contribution to the auto industry with respect to innovation.
Toyota - kazen & lean production
Mercedes Benz - safety, implementing new technology, patients (e.g. weight reduction on bolts)
Tesla - proof that electric vehicles are feasible and the way of the future / now
I can't think of 2 others, will edit when I can.
Ford would have been an obvious one with respect to the moving production line but in retrospect it has not been the best method for a variety of reasons (cost, inventory mismanagement, labour relations).