Albeit kept stock, this deserves an honorable mention because it has an engine made out of two engines (2 inline 6s). And that is enough to be mentioned here.
https://www.caranddriver.com/news/a43435570/tvr-cerbera-speed-twelve-auction
https://www.caranddriver.com/news/a43435570/tvr-cerbera-speed-twelve-auction
Car and Driver
One-off TVR Cerbera Speed 12 Deemed Too Wild for Production Can Be Yours
This English mad dog is coming up for auction in May.