Birthers

I think the passive-aggressive ones -- with Tom Maguire being the supreme example -- are my favorites. Although sometimes you have to prefer the undiluted variety; i.e. "[the transparently fake alleged birth certificate from a country that didn't exist when it was issued is] from WND, but appears legit."

In, fairness, though, the birthers do have Larry Johnson on their side, which always heightens credibility!