Well, for me, and for my future projects, I would have to say orange ghost and butter.

Butter lends a soft but intense yellow creamy look to most morphs, and orange ghost further amplifies this softness by giving everything an almost velvety appearence. My male butter orange ghost really shows this, and his yellow isn't fading with age like a normal butter, instead it is becoming a lighter almost glowing yellow. I'm hoping to start a project that will add these two genes to other combos to lend this effect.