Skull Kid is intriguing, I guess I would say. He possesses probably one of the better "villain stories" in the Zelda series, if you know what I mean. Ganon is your ordinary antagonist, the one that's just there, like a Bowser, a Ridley, etc. While Vaati is cool and all, I also kind of find the story behind him kind of boring. However, I find it kind of cool that Skull Kid was your ordinary little boy, but stumbled upon this commodity we like to call "Majora's Mask", and proceeded to nearly destroy the world by making the moon crash into the Earth. He ain't after no princess, he ain't after no world domination, he's after straight-up apocalyptic world destruction. Sure, many of the other characters in MM stand out when compared to other characters in the Zelda series, and MM holds the best group of characters in general in my opinion, but Skull Kid is one beastly little boy if I say so myself.