What do people think are the grossest scenes in South Park?
I thought that Butters getting a liposuction in "Jared has Aids" was pretty gross. Little bits of white and red tissue coming out of the end of a hose, splattering all over the place, Stan pushing down on Butters to make it come out faster, and Butters slowly deflating.
The fake (and dead) Kenny being birthed by Ms. Crabtree in "Fat Camp" was pretty gross, too, but not as bad as the liposuction.
Kyle popping his hemorrhoid going over the fence in "Cartmanland" elicits a sympathetic reaction, because it's done so plausibly, and Kyle crying for his hemorrhoid cream is acted so well.
Any others?