Costa Rica
Many countries can claim to be famous for their coffee, but perhaps Columbia is the head of the list.
Wikipedia lists its colour as "finest white."
Canada
I know it was his most famous.
'Finest' is a matter of judgement. You should buy the man-made diamond that you can afford for the purpose you require. Read more, below.
The finest rubies typically come from Myanmar (formerly known as Burma). Myanmar has a long history of producing high-quality rubies known for their intense red color and consistency.
Iceland
sierraleone
Mozart's finest and probably most famous German opera was The Magic Flute.
Senegal
The Smith mountain quarries in Arkansas are famous for producing the worlds finest sharpening stones.