When I babysat for the kids in the neighborhood, way back in the day, we had to walk to and from school in the snow, uphill both ways (it was actually--now that I think about it). The one thing I was famous for was being the "tickle monster". I'd tickle the stuffing out of every kid I knew, until they almost peed their pants. It was my thing. They'd laugh and laugh and yell, "Do it again! Again!" And I'd humor them until they started turning purple from lack of oxygen. Good times.
Now Rick is Ada's #1 tickle monster. He's really good at it too. I can honestly say, I taught him everything he knows. :)
Moral of the story: Few people in the world really, truly hate being tickled. Beware of those people and have fun with the rest.