Jerzy Michal Sadlowski
Jerzy Michal Sadlowski voted up Didge Doo's answer

I've been sitting here trying to recall the very worst thing but those nasties have erased themselves from my memory. And so, even though this may sound un-Australian, I'll list one of my pet aversions. VEGEMITE  Can't stand the stuff.

But it tastes just fine when added to stews. :)