When my sister and I were young I used to torture her 3 different ways. The first way of torturing her is when I would always goose her every chance I got. I would sneak up on her and goose her and she would jump. I would wet my finger and put my finger in her ear. Finally I would sneak behind her and squeeze her buttocks, just one big squeeze.
This went on for a couple of months and then I stopped torturing her. It was fun for me anyway. It was never brought up again.