my new favorite type of vodka is Żubrówka (or Bison Grass)
I had it for the first time a few weekends ago when friends who had been in Poland for a wedding dropped in to visit.
Its FANTASTIC. Had it over ice, and it was wonderfully drinkable.
As to the earlier poster who spoke about filtering vodka...
You can filter vodka yourself at home! All you have to do is take a cheap brand, run it through a Brita pitcher a few times, and you end up with a much better tasting vodka.