Jigen666

That's a trick question. Does "best" mean most desired by shoppers? Best rated? Or, best value for the $?

Most desired is probably the Yamazaki 25 Limited Edition (AKA Yamazaki 25 in a fancier bottle), at an overpriced 250,000 yen. It pops up every so often at Narita Duty Free. While it is about 100,000 yen higher than it's non-fancy bottle version, the regular version has been nigh-impossible to find in Japanese stores (save for the few lone shops that have jacked it up to crazy prices). The Hibiki 30 is probably also on the high demand list. There's also the Taketsuru 25, but I believe that's gone the way of the Dodo.

Best rated, I couldn't say? Again depends on your price range. I'm sure there are those who will swear by the Yama 25 as the best product of Japan. But others might tell you that the Yama 18 is just as good and 1/5 the price in duty free. Others might tell you the blended malts like the Hibiki 17 & 21 are excellent choices. But again way overpriced compared to their retail store brothers.

Best value for the $ (or yen), there's one I can tell you that's actually cheaper in Duty Free than any retail store in Japan, and that's the Nikka Taketsuru 21, which is 13,400 yen Tax free. Most retail shops sell it between 14,500 and 15,000 before tax. It's one of the only things that is actually cheaper in Duty Free than retail.