I've seen this thread come and go before, so I'm gonna try to be a little more distinct than I've been in the past, but that might not be that easy since my opinions are kinda tepid on the topic; I like most tropes, even some of the ones that seem to trigger people sometimes (ridiculous stuff like 'and now you'll be 1000x more ticklish and you'll be tickled for 1000000 years nonstop!!!' like OP says, etc.) and most my active dislikes are reasonable and common enough (floating feathers bad, amirite?) that they don't really bear talking about. But anyways, here goes.
I really like this one, even if there's not really a name for it, that I know of, but I think you'll know what I'm talking about if you follow along. I'm gonna ironically call it true tickle magic and I'm gonna add true sci-fi tickle technology in the same boat. And as a short description I'll say 'concepts in tickle smut that aren't realistic or even possible within our world, that result in tickling that is different and more intense than common tickle experiences'.
Or as another possible way of looking at it, tickling that comes from magic or scifi tech, that isn't just trying to emulate the way humans tickle each other already, ie., tickle spells that just summon magic feathers, tickle machines that simply have spinning brushes pressed agains the 'lee's tickle spots, or truly the most basic of all, magic hands/white-gloved robot hands that just tickle with regular fingers, and that's that. Nothing really against any of these, but they don't bring a lot to the table that a human or a bunch of them couldn't in a regular, non-magic, non-scifi setting, and thus they're not what I'm talking about.
What I am talking about, is rictusempra (or spells along that line), that enchant your very nerves so they feel disarmingly ticklish. Or tickle prods, machines that send powerful electric shocks that don't feel painful, just ticklish, when used on a victim's body. Or tickle slimes, monsters that trigger any skin they come in contact with to make it feel like every inch of it is being tickle tortured. Or tickle hacking, to remotely trigger ticklish sensations on an android or a cybernetically enhanced person from within the very programming of their tickle spots. Or an eldritch deity of tickle torture that can burrow it's influence into your very being to skewer you with searing tickle magnitudes that would break your feeble mortal mind in fractions of a second.
Or the Spongebob tickle belt.
As far as why I like it, I think it's partly because of the alien nature of it (which I imagine probably makes some people dislike it), that just makes it more exciting and easy to let your imagination run wild with, and also, and this is the big one, because it sells me on how intense it could be in a way that realistic, easily understandable tickle stuff can't, and I love intensity. Like, just think about it: a single hand using five fingers on a tickle spot, the most baseline simplistic tickle tool, compared to an electric current specifically designed to target your nerve endings directly and deliver an overwhelming ticklish sensation straight to the source of it. It's like comparing the effect of a punch to that of a stun gun. Same for a tickle spell. Maybe if you hit a certain cutie from Slytherin with rictusempra from afar you can bring them to their knees convulsing with laughter, but maybe if you tie them down, forcefully press your wand against her exposed armpit and cast it, it'll break her brain with ticklish sensations for the next couple of minutes. The sky is the limit, when we're not being tied down by floating tickle feathers and brushes.
Another aspect I dig is the idea of remote tickling that could come from it, specially of the unrestrained variety. Like a slime getting in the back your shirt or your boot, and you ending up spreading it all over you in an attempt to wipe it away, or a poor robot that's never experienced the sensation having it's receptors forced to receive it non-stop while it writhes in ticklish agony, or a more elegant version of the tickle belt that can be attached to the base of the neck of a cute prisoner to make her easy to subdue at the press of a button, and that won't stop tickling her until she's been deemed adequately submissive. Tickling you can't get away from even if you're not tied down is goated.
TL;DR: unrealistic and impossible but extremely intense and effective tickling the way that can only exist in fiction.