I'd have to say being on the cleaning crew of a slaughterhouse:
Excerpt from Fast Food Nation:
"When a sanitation crew arrives at a meatpacking plant....
Three to four thousand cattle, each weighing about a thousand
pounds have been slaughtered that day... The place has to be clean by
sunrise... Workers climb ladders with hoses and spray the catwalks. They get
under tables and converyor belts, climbing right into the bloody muck,
cleaning out grease, fat, manure, leftover scraps of meat."