I like when every touch makes them twitchy. I have a ticklish belly and when i get poked or pinched there, my stomach involuntarily retracts. If I see that on someone, I can feel it tickle just watching them.
As far as separate movements, shaking of the hands and head are funny because the sensation crawls up the body and its uncomfortable, you can'tdo anything with it. Or when the parts not in attention try to run away—the upperbody bucks and rolls when you tickle their feet, or for me, my knees go weak sometimes.