So...I'm really bad at ranking things like this because it fluctuates a lot so take this list more as a list of pairing I really enjoy than a ranking from top to bottom:

• Boogyu. They weren't the first pair I got into and it's always a battle in my head (and fics) between them and Verkwan but luckily I can enjoy a fleet of ships, but I feel like for all the food that is out there they don't get enough love from the fic community
  
• Verkwan. They're just...so...soulmate-y. And sometimes my Verkwan feels waver or die down a bit and then suddenly BAM they do something that is so THEM and I fall all over again (BONUS mention for Verkwangyu! Technically not a 'pair' but more people need to consider it)
• Jeonghoon. They are secretly #1 on my "ships that make me feel INSANE" ranking
• more recently: Jeongkwan. They are married. Jeonghan is in love and doesn't always know how to express his feelings with words, but he is in love.
• Soonwoo. There is something about them that just FITS
• Cheolhao. SOMEONE (I hope you know who you are) has really shown me the light and they are so tender and supportive with each other
• Jeongchan!!!
• Boochan! I was blind to them for a while but my eyes are OPEN now
• Seoksoon. They are insane, more so when they are together.

Anyway.... throw any BSK pairing at me and I'll enjoy it (Boojun, Booshua, 2seung, I'll eat that right up!) I also very much enjoy having my eyes opened to dynamics of rare pairs because it is so much more fun if you can go a little delulu insane over the smallest interactions, lol.