Here in Tennessee, we don't register by party affiliation, so when the Republican candidate has the nomination wrapped up, I always vote for the absolute whackiest candidate in the Democratic primary. I think it helps keep the Democrats fielding the most bizarre ideas imaginable and makes them think that their finge looneys have real support. I like to think, for example, that my vote for Howard Dean in the '04 primary helped make him DNC Chairman.
I like causing mischief too. Once I voted for Jesse Jackson in a primary election!!!