From what you list, I would say Leopard or Enchi. If I were to add my own option I would throw out OD.

While I get why a lot of people like YB or BluEL group or Fire for what they do as single genes, I tend to find that once they become pervasive in your collection they are more of a hindrance. As an example, next season I have two animals that I could pair together that would offer me 324 possible outcomes one of which would be a quad superform... But two of those possible superforms are BluEL and Ivory. And in just about every case, if I make a BluEL or an Ivory I will most likely have zero idea what other genes it may be carrying so I either have to keep all of them back to prove them out or move them out as only the base superform, potentially giving out a powerhouse animal. Neither of those options appeal to me, rendering what some might call a fantastic pairing opportunity utterly worthless.