So many very good designers (has anyone mentioned Alexander Kartveli yet?) but one does stand out, particularly considering his later accomplishments. Kelly Johnson.
The question of manufacturer is a little more difficult, as many organizations only produced one really outstanding aircraft. Those that consistently produced exceptional designs would include (in no particular order) Lockheed, Boeing, Douglas, North American, Avro, Hawker, MiG, Tupelov, Messerschmitt......