I really like the outer look of the Heavy Ball, Lure Ball, Moon Ball, and Cherish Balls.
The opening animation of the Beast Ball and Timer Balls are great.
Utility wise Quick Balls and Dusk Balls are usually the best, barring hacking in 999 Master Balls.
Overall favorites are the Heavy Ball, Moon Ball, and Beast Ball. Premier is nice too. Cherish ball would be among them if not event only.