An insanely, unbelievably ticklish tickler.
There's the revenge thing, of course, but it's also ....I guess a whole different psychological aspect that I can clearly comprehend, but can't express in words....wish I had a bigger vocabulary I guess!
It's kind of a "playing with fire" thing - playing with fire is good and exciting, until you get burned. (yet it's not like that, because the ticklee doesn't get hurt...and no, getting burned by fire is TOTALLY different than be tickled....)
But if someone's is playing with fire....yet can't be burned, let's assume they were superhuman, or metal, or whatever...it become totally different, there's almost no interest there. "Big deal, he's playing with fire...it's not like he can ever be burned!"
A non-ticklish tickler isn't nearly as exciting as a ticklish one, it's boring, because there can be no revenge, so you may as well have a machine doing the tickling.
I think it's the DANGER that makes it so much more interesting. You think, "Yeah, she's enjoying tickling poor girl...but if SHE gets the tables turned, watch out!"
That's why, still, one of the greatest tickling videos of all time was TIB's "Nurse Gone Bad." starring one of the top ten models ever, Rachelle Smith.
(yeah, I was hard on him in another thread...but great art is still great art.)
The story was, this crazy nurse, who is insanely ticklish, has kidnapped a girl and tickles her every night. The girl is moderately ticklish. She of course, escapes, (thank God!) and then tickles the nurse, who goes wild with laughter. While the nurse tickled her captive, the camera would pan down every now and then to her stockings and shoes, as if to say "Yes, go ahead and enjoy it, because soon those feet will soon have fingers dragged across them..."
Not that I'm AGAINST a non-ticklish tickler. I know some models simply aren't ticklish, but want to help with videos, so have to be the tickler. I'd rather have that than no video!