Heal Balls are one of the better looking varieties, in my book. The only competition is Premier Balls and the (unfortunately not available to most players) Cherish Balls. Unfortunately, I'm boring, so most of the members of my Emerald/Pearl teams were caught with more traditional fare. At least Ash (my first Gardevoir) is in a Nest Ball, I suppose, those are kinda nice.
I should use Heal Balls more often in the future~