Snow Queen is the smoothest best tasting vodka I ever had, hands down.
Snow Queen is by far the best vodka I've ever had too, so smooth it's ridiculous. However, seeing as it is a Kazakh vodka I don't think it counts as a Polish vodka ;)
Zubrowka is easily my favourite Polish vodka if I'm having it with apple juice.
If I'm just shotting vodka then I'd probably go for Pan Tadeusz.