I think GP means forgettable in the US. Here is the brands from the Wikipedia article:

  - Abarth
  - Alfa Romeo
  - Chrysler
  - Citroën
  - Dodge
  - DS Automobiles
  - Fiat
  - Jeep
  - Lancia
  - Maserati
  - Opel
  - Peugeot
  - Ram Trucks
  - Vauxhall

None of them I would call "forgettable". Most of these brands have been there for more than a century. The only ones more recent than that are Abarth, DS and Ram. DS and Ram refer to iconic vehicles by Citroën and Dodge respectively and lately turned into their own brands.