How do you pick one? But I like words that cannot be adequately rendered in English (and also diminuitives, because they don't exist in English).

For example, see авось or пошлость. On poshlost, if you like literature, check out the interview with Nabokov, question on page 12, or, at more length, Nabokov's book on Nikolai Gogol.

I also like каша because buckwheat is delicious and nutritious!