I was in the theatre group back in high school, and the paint we used for backdrops and set pieces was without a doubt the worst thing I've ever smelled. I think it was "Iddings" paint, but we all called it cancer paint. Why we called it that depended on when you asked - sometimes it caused cancer, sometimes cancer was a preferable mode of death, sometimes cancer was a primary ingredient, along with damned souls and horse hooves. It smelled like diarrhea, but worse, and the stench got everywhere, out into the halls and into neighboring rooms. And once we touched it, the smell didn't leave our hands for days.