That really depends on whether the genes are recessive, co-dom or dominant and what is already in your collection.
A HumbleBee to breed to my OG, and a Red Axanthic are high on the wish list.
The work Corey Woods has done with his RA's really got me thinking about the possibilities.
The Desert gene is another I like just not enamoured with the females being sterile and potentially dying if attempting to breed them.