I'm a big fan of namazake, which is unpasteurized sake. These sakes do not last as long as regular sake; they tend to go bad and smell cheesy quicker than pasteurized sakes, but if you catch them at the right time, they are beautiful. Namazakes need special care-- they must be cold shipped and stored, similar to fresh produce. I've heard some sake experts say that they do not prefer namazake because the purity is hidden, and I find it curious that this is the very reason why I prefer namazake; I think they taste "purer," and here I put "pure" in quotes because this term brings with it a lot of culturally charged baggage that can have different meaning among different people.
To me, namazakes have a dancing texture to them, a life, a liveliness that you don't find in pasteurized sakes. Yes, there are plenty of incredible pasteurized sakes that I've been moved by, but there is something about the almost electric intensity of namazake that I find appealing. I find this same vibrancy in unfiltered, low-sulphured wines that undergo the same minimal preservative treatments as namazakes.
This brings me to one of my favorite namazakes:
Eiko Fuji namazake junmai ginjo (Yamagata, Japan)
Yamagata prefecture is on Honshu Island in the Tohoku region. It faces the Sea of Japan on the west side, and is separated from other prefectures by mountain ranges that are speckled with interesting geographical features, such as volcanoes, and Goshiki Numa, the "Five Color Lake," a crater lake that changes color based on the weather.
Define "purity" as you will, but this is sure to fall under your category of "delicious."