Starline for me. Espio and Cream don't have very interesting personalities, Zazz and Jet veer towards "annoying" rather than "fun", and while Tails has a more established personality than the aforementioned characters, I wouldn't really use "fun" to describe it

All of em

A tie between Cream and Tails. (I voted Tails though)

Out of these, yeah, Starline, for me. Just like Starscream from the live-action Transformers. Sycophantic, but later on, treasonous.