I wanna say that black with gold probably has the most die hard fans out there. Personally, I lean towards anything with silver or ruthenium hardware (or that so-black, which is also TDF!) just because that's what works for my style, wardrobe, skin-tone, etc. But I definitely think there are certain bag styles and colors that look better with gold hardware.
In my opinion
The most iconic combination: black m/l lambskin double flap with gold HW
The most popular combination today: black caviar jumbo double flap with gold HW
The one that I would want if can have only one: 15C pearly charcoal m/l caviar with ruthenium HW
If I could have second one in addition to first: 16C irrediscent goat small boy with rainbow HW