Nominating Whimsicott for A rank, give or take; it's a ball of cotton and a fairy, how can that not be cute? Taunt costs it some points, because Taunt is definitely not cute. Encore is cute, though, as is Moonblast.
(And yes, Whimsicott is on the actual viability rankings, B rank, in fact.)
edit: woo, 0.650k posts