shaco, anivia, ezreal, lee sin, nidalee, twisted fate, kassadin, and cass.. i'm sure im missing some people ^^.
From my experience these threee have a high skill cap.
Ez because if you miss his skill shots, hes fail so its takes time to combo his spells all while remembering to autoattack.
nidalee because of her panther form/human form uses. YOu have to properly know when yo go into panther mode to stomp on people and when to be in human form to heal/ be a factor teamwise.