Well I have yet to decide what I will wear for Halloween this year, but I have certainly come across a few worthy candidates.
The Holy Sh!t costume
(if you scroll to the bottom of the page you will also find numerous other good costumes such as 'hung like a horse' and 'man eating shark')
Or the interactively entertaining:
Super Snake Arcade Console costume
Here's another one that's pretty creative, but I think its geared more towards the ladies:
Pigs In A Blanket
Currently, the Holy Sh!t outfit seems to be the most feasible and funny outfit that I could make and wear, so that might just be my candidate.