Andy, at least it wasn't the 250 Villiers!

My "Biggest with the smallest" would have to be a 1960's Fiat Multipla - 600 cc, 6 seats, and the only car I have driven at wide open throttle for prolonged periods, at probably about 45mph.  It was not my own, but a work car that my dad would bring home occasionally.  

 

This period was also the only other time I have driven a Skoda - a 1960's Octavia, which I remember mainly for the very heavy steering. 

 

Largest in terms of engine size would be Holden Commodore with a 3.8litre V6 (currently used by 'er indoors).