difficult...
the quattro because it began 4wd
the quattro s1 for the fantastic looks and that noise!
205t16 e2 because it was so good everywhere and was so light with spaceframe chassis (i think it also had a primitive antilag system)
delta s4 because it was mad. supercharged and turbocharged, spaceframe also
rs 200 because it had so much potential
i just like all of them...