I am searching for a good english word that would be an analogy for russian word izuminka, direct translation is raisin, but it is used in figurative sense.
Other synonyms I've found: appeal, picanthy, zest.
Most close meaning would be an interesting feature.
So it is something that makes the object not so common and this single feature tends to add an improvement, mostly when speaking about visual appeal or taste.
E.g.: "She is not exactly an attractive woman, but she has an ... "
Also it should be possible to use the same word in ironical sense, so if put in quotes it becomes a mockery:
For example a new website or software feature:
A: What is this new annoying feature?
B: You don't get it, this is a "..."
Or nitpicking about someone's look:
A: Why does she wear these ugly yellow shoes?
B: It is sort of her "..."