When small car companies need to keep their costs down, they generally turn to larger OEM manufacturers for a pair of rear lights or the side mirrors. This means that the headlights of an econobox might pop up on a supercar or the side mirrors of a brown, 5-cyliner diesel, AWD family wagon might be the same as the one of a luxury grand tourer. I've tried to keep out some of the parts binning (otherwise we'll be stuck in the VAG loophole), but he's some stuff that I've found.
GT40 rear lights come from a Chevrolet Corvair because speed
Noble M400's rear lights come from a Hyundai Sonata
Lamborghini Diablo has Nissan 300ZX headlights
Later models of the GT40's rear lights are shared with the Fiat 850, Lancia Stratos, and Lancia 037
McLaren F1 has the same wing mirrors as a VW Corrardo
The independently developed New Stratos concept has the same rear lights as the 599