I have friends who swear by the technique of passing the cheapest handle of vodka one can buy through a Brita filter four times. They say that, after filtration, they can no longer distinguish between it and top-shelf stuff.
I'm about to try it (it's not actually cheaper for me, because I didn't own a Brita filter to begin with), but am curious if I'll poison my New Year's party guests by serving them the stuff that comes out of it. Has anyone else done this? The Internet at large seems to have mixed reviews.