In the uniqueness tier list he is in S tier, behind only Lip and Zoroark. Nobody told me why Zoroark, Lip, and Chibi Robo were up there. Anyone know? I don't know much about them.
Chibi-Robo would be fun for both gameplay and moveset. As far as gameplay goes, you could make a joke out of his size, much like Little Mac and Olimar. He is equipped with a blaster and copter, which make for obvious special moves, while his primary function is using ordinary objects to clean. It would be fun, for instance, for him to pull out a giant toothbrush to scrub opponents with, with the intent of cleaning them in mind but instead doing damage.
Zoroark has a lot of potential. As a Pokemon, he is Dark type, so that in itself has a pretty big movepool of attacks we have yet to see in SSB. Aside from that, Zoroark is known for it's trickery and Illusion ability. Many Dark-type moves play upon tricks and could have interesting translations into SSB, and the Illusion ability has a lot of potential incorporations.
Lip has many references to both her game and her character to work with. As she stands, she is a plant themed character, which opens her up to an elemental type of moveset of which we have yet to see. Special moves can make use of the functions present in Panel de Pon, such as garbage blocks. Meanwhile, many fancy the prospect of her using Lip's Stick, which has already been in SSB, as a gameplay aspect with similar functionality to the item; use weaker attacks that drain the opponent's health over time; a fighting style we have yet to see in Super Smash Bros.