How about a dog's tounge? My golden retriever used to lick my feet, and it felt incredibly ticklish.
Another dog's tounge story, and forgive me if this is a repost. One time, many years ago, my best friend's mother, who is now in her 60s, but who supposedly had very ticklish feet at one time, accidently spilled cereal on the floor. The family dog went over to eat the cereal, some of which had spilled on my friend's mother's toes, and the dog began licking her feet and toes. Supposedly, the woman went ballistic, and began laughing hysterically, because the dog's tounge tickled like mad.
Those are two interesting instances of a dog's tounge feeling really ticklish.
Mitch