The top four for me:
Subaru Impreza with the blue livery
image from
http://cube.ftyczka.org/subaru/
Ford RS200 from 1986
image from
Turbocharger.Co.Uk
Toyota Celica 1992-1994 with Castrol livery
image from
http://www9.plala.or.jp/naoki1975/na...ca/cerica.html
Lancia Delta Integrale with Martini livery
image from
La Storia del Rallye di San Remo
-Sam Damage[/img]
edit: added images