Corsodyl mouth wash, the one where the woman takes her false teeth out. Not so much because of that, but because the cover of Tainted Love actually gets the words wrong!
I'll go with you on that gross ad "Go Compare". Not too far behind that I would put those really irritating ads for Harvey furniture just before the start and during the halftime breaks before Corrie - they're not remotely funny, but just stupid. I've one more to add later on as well. :)