Scott Roeben at Dribbleglass.com came up with this list of Politically Incorrect Halloween Costumes:
Cave man. The proper term should be "evolutionally challenged"; "man" is overtly sexist; also insulting to those in loincloths.
Pirate. Distasteful to those with hooks for hands and the vision impaired (wearers of eye patches), not to mention parrot owners.
Dracula. Endorses the irresponsible practice of transmitting bodily fluids.
Clown. Deeply offensive to Geraldo Rivera.
Hobo. Derides the economically and hygienically disadvantaged.
Indian. Native-Americans have been oppressed, slaughtered and persecuted—imitation buckskin and feathers are the final insult.
Napoleon. Offends the French. (In much the same way deodorant does.)