The one that I drink the most is Tito's. Its made in Austin, TX...but is the best and smoothest I have tried. I have served it (I am a bartender at a country club) side by side with grey goose and nobody could tell them apart.
On my UK trip last fall I discovered Zubrowka, a Bison grass Vodka from Poland. Delicious (and this coming from someone who didn't think he would ever enjoy Vodka again after abusing the thing many many years ago)!
I was surprised to see that it was available in our state owned liquor store back in Montreal, albeit in a slightly different bottle:
Edit: Just saw that bone already mentioned that one
I found it on a trip to Canada several years ago. It wasn't until much later that they started importing it to the U.S. When I first found it here I asked the clerk how long they had had it in stock, he said 4 hours. Now it has become hard to find again. Thankfully my local store has it.
The problem is of course that it totally disappears when mixed, which led to me downing a liter in a couple of hours...that did not end well. It's not that good straight though.