I always found Sonic's taunt most amusing right before someone fell of an edge or ran into something harmful as him. His speed makes steering him a bit tricky. XD
I've actually managed to do very well as him, having never played him much before. Hyper Sonic's even faster, but the most deadly of all Final Smashes, IMO. And yeah, it would be amusing. I always use it whenever no-one can hurt me, though. =P