Quinn core ?

She's the only ADC who can hit the level of movement speed she can, and I think the only champion who can sustain that speed indefinitely. She's also probably got the highest burst of any ADC. While she is a marksman, she's played a lot more like an assassin, flanking to the sides and using Valor + her crit build to straight 1-shot people.

For items on her, I like Ghostblade, Duskblade, IE, Statikk, and either Tri Force or a second Zeal item. Mobi boots, of course.