Fiat last offered a two-cylinder car in the early 1990s when the antique Fiat 126 Bis was still around. Against all expectations, engineers in Turin revived the notion in 2011 with the TwinAir engine. It sounds like a blender at tickover, and a twin-prop plane at speed, but it's always truly hilarious. On paper, it's ultra-economical (up to 3.3L/100km), but in real life, no-one has yet managed to match that. Still: what a laugh.