The type of waves likely wouldn't vary too much from person to person unless you factor in that some tickling to some people can be relaxing. But if you mean in an intense tickling situation where the person would be under "stress", then, as QueenBeeBeeMari has said, it would likely be Beta waves. I don't believe (though I could be wrong) that the variability of whether or not the tickling is pleasureable has as much to do with it as does the degree of the stimulus itself. In other words, whether very pleasureable, or very painful, the body would still be recieving a high level of stimulus, therefore, it would likely fit into the brain wave catagorey that best relates to awareness. If all of that is correct then the Hertz can then be narrowed down. Beta waves oscillate at a broader range than the other waves (13-40 cycles per second, or 13-40 Hz), but it does still give a narrower margin than before. The exact measurement in Hertz is likely variable upon the degree of the ticklishness, the trust between the tickler & ticklee, the general fear level, the severity of the tickling, etc. Though an average could likely be calculated, I do not presently know of any records on the subject that could be used to give any accuracy. Well, that is my take on the matter. Hope this helps.
FYI EDIT: I forgot to mention that if studies confirmed this hypothesis, measurement of increased brianwave activity could easily be used to identify if a person was really ticklish or just faking it.
