Out of the choices given, I'd have to say "sometimes." Clearly most, if not all of us have a strange fascination with tickling. But its very contextual. Is seeing a woman in a bikini sexual? Not if she's your sister, or a purely platonic friend. If I'm not attracted to the person, its more just harmlessly flirtatious. That being said, tickling a woman I am attracted to is significantly sexual, and has definite potential to get me going, so to speak. It also depends on how she reacts to it. Maybe a better answer than sometimes is "usually."