Gordon Murray would have to feature quite prominently in that list. He was of course not an Engineer but a Draughtsman with a serious aptitude for car design. He learned his engineering skills along the way. He trained at Natal Technical College in South Africa. It is now the Natal Techinal University who honoured him with a Professorship in 2002.
He designed the Brabham BT46B Fan Car and the championship winning BT49 and BT52.
He was a bit too adventurous with the BT55 but he used the concept to good effect on the MP4/4, the first post Barnard McLaren (barnard had moved to Ferrari in 1987) and it remains the most successful GP car in history winning 15 out of 16 races.
The MP4/5 family of McLarens F1 cars was his work as well and literally dominated F1 in the hands of Alain Prost and Aayrton Senna from 1989 to 1991. He moved to McLaren cars thereafter and penned the awesome Mclaren F1 road car.
I believe he was also instrumental in the Ariel Atom by designing a predessessor called the Rocket, a similar car that the Atom was based on
The man is an automotive genius. He designed his cars on a drawing board and largely by himself (especially in the Brabham days cos Bernie was tight even then).
Between himself, Adrian Newey and Rory Byrne, they have dominated F1 over the last 30years.
He and Byrne are of course, my countrymen.