Yy to finger sucking, scraping out yoghurts and any scraping of the last remnants of food. grrrrr.
I can't bear any noisiness when eating or clashing of cutlery on teeth, or open mouthed eating, or drinking when there is food in the mouth. I could go on and on and on.
I have ruined my children; they now notice other diners bad table manners in restaurants 
I hate, possibly more than anything, when people eat a spoonful of ice cream and bring the spoon out of their mouths with ice cream still on it, usually in a rounded shape. This makes me want to heave.