Here's some stuff I posted in a similar thread way back when
1. Simplicius Simplicissimus: Old (enlightenment era) German book, lots of translations in English in academic libraries. In the chapter when the soldiers take his grandfather's farm, the naive narrator describes that his grandfather was lucky because he confessed with a laugh what others were tortured for. The soldiers tied him down, spread salt on the soles of his feet, and let their goat lick it off, which "so tickled my knan he nearly burst laughing."
2. The big-time Oprah book "She's Come Undone" has a couple of scenes when the narrator gets her feet tickled by a guy. Kind of a downer, though, because I think he turns out to be a rapist.
3. The Erskine Caldwell short story "Pa and the Grass Widow" has the closest thing to sexual tickling I've seen in a mainstream book. A young boy goes to find his pa and finds him with the grass widow, a pretty young lady who has taken her shoes and stockings off while he tickles her bare toes with a chicken feather. He dwells on this quite a bit, and the father is jumping with glee whenever her squeals reach a certain pitch.
4. A couple more comics: the japanese comic "Barefoot Gen" has a scene in which the title character is tied up and his brother tickles his feet. Do with that what you will. Also, the adult comic "Ironwood" (by the same folks who put out "The Blonde" has a brief tickle in vol. 1, when two women are having sex and one sucks the other's toes, making her yell, "stop! that tickles!"
There's also a play by George Bernard Shaw that mentions tickling a lot, in an F/F context. One character is threatened with tickling and pulls her feet up under her in fear.
That's all I can think of for now.
