I'd say the Rebel Transport X-wings, specifically Tarn and Wes and how amazing they are in the currently 2 ship meta.
Other than them, though, definitely the shuttle. Haven't seen one put on the table in ages, most likely because the dial scares players off or because it's inconceivable to field a large ship with an arc anymore. Doesn't make them any less cost efficient or incredibly accurate (FCS + Gunner, or just good ole Vader), though.