3 top candidates are "Shave em dry" by Lucille Bogan which is not only hilarious but also completely disgusting "Reefer Man" by the Harlem Hamfats and also a Welsh guy singing When I'm doing acid to the George Formby tune about window cleaning. The Stash record label has literally dozens of hilarious songs relating to sex, pot smoking and other vices.
Your balls hang down like an old bell saddle, your dick stands up like a steeple,
Your goddam arsehole stands open like a church door and the crabs walk in like people - Top that (Lucille Bogan Shave em dry)