Stomach, ribs, neck, knees, and especially the arches of my feet. I've got high arches, so nothing ever touches them. I was clenching my teeth and forcing myself to sit still last time I was dragged along for a pedicure. 

I don't think my boyfriend will ever try to take advantage of my ticklishness. He'd get punched by the flailing limb of an exceptionally tall individual if he did.