I don't know what it is about being relentlessly tickled -- must be the way the nonstop urgency of the sensations short-circuit your logic and decision-making -- but it often drives me to make the kinds of obvious, unnecessary, counterproductive statements that others are mentioning in this thread -- "No no, nonono, I'm so ticklish," or "C'mon, c'mon, I'm a very ticklish person, stop," or "I'm really ticklish there" or "My sides are really ticklish STOP." Basically narrating things the person you're talking to is absolutely, completely, 100% empirically already fully aware of.