Dark Qiviut

My order of quests from favorite to least:

1. Pinkie: The most complete, one of the funniest, and really well done as a whole. Her chemistry with Rutherford and the reindeer is excellent. Her characterization in itself some of the best of the series.
2. Twilight: Really funny with classic Twilight at her most relatable.
3. Spike: If he didn't decide to switch and become a lovesick buffoon, this would've been decent. If he either kept his card or had Rarity's originally, I wouldn't have any issues. Plus, it would've been nicer to see more of his thought process as he crafted his present. Would've delved more into his mind and make his quest to trade earlier sound more meaningful instead of lustful.
4. Dash & Discord: The beginning was really good and funny, and their chemistry grew naturally. Even Discord's winterzilla gift had good intentions here, unlike his act from 3's a Crowd, What About Discord?, and AMoP. But wild animals belong in the wild. He doesn't belong in the sanctuary without a good reason, and no, that "he's alone" copout doesn't cut it!
5. Rarity: A mixture of great and atrocious. The great is Rarity meeting Pistachio and his parents in Sweet Acorn Orchard and, despite him knowing it belonged to someone else, let him keep it, staying true to the spirit of not just Rarity, but Christmas, too. Unfortunately, Derpy's mistake set off her subplot, and her out-of-character, ableist portrayal's one of the ten — if not five — worst moments of the entire series. Her cameo was offensive and hurtful. Because her error directed affected the plot, Rarity's generosity's really soiled, too.
6. AJ & Fluttershy: Wasteful and pointless, marred by FS being out of character. You can read why here.