For your Exp. 25, I remember reading a fiction story on this site many years ago which the Monopoly board was drawn on the tickle victim's belly, which was ticklish enough on its own. Then the game of Tickle Monopoly began.
I personally like the Oral B Pulsar disposable electric toothbrushes for tickling. The plastic pieces in the bristles add a good intensity.
http://www.oralb.com/products/pulsar-toothbrush/