I've got my own list:
the kitchen sink drainer, between the gasket and the underside of the basket--ick! (I pry open the join with table knife and wedge in my scouring cloth; awkward at best.
the inside of the disposal and the underside of the rubber opening of same--double ick--grind a couple of halved lemons, then use the scouring cloth which I then throw away or bleach.
the roller-cutter on the can opener--scouring cloth and toothbrush dipped in 10% bleach
All these places that organic materials congregate are like toga parties for bacteria so I try to keep up on them but every once in a while they really gross me out.
Please post your 'horror areas' and how you deal with them! There must be some better ways to tackle those problem areas so we can cook in a more healthful environment.