Heh. That kind of sounds like me, Arson. :blush
I can usually ignore it if someone's just rubbing their fingers up my feet - and I used to get reflexology every week, and love it, my feet are so sensitive - but if anything more sharp, like a fingernail, would even lightly scratch my sole, it makes my foot jerk, trying to escape.
If it's more than just a quick 'scratch' by mishap, then I'm about ready to KILL you if I can't get my foot away if it's for too long time (more than two, or one, seconds :blush :blush :blush :blush). It just tickles too TOO much!! >_<
Note, I'm 21 years old and have never ever EVER EVER EVER had my feet tickled for more than, four seconds, maybe. (And those four seconds were torture, trying to seem like nothing's going on and continue watching TV!!!! :scared :scared) And yes, I DO plan on keeping it that way for as long as I still can! >_< >_<
So, Arson, if anyone ever'd tickle my feet for, likely however you end up tickling this girls' feet for, I'd reply with the same witty comeback (Shut U-uhuhuuupp!!), and then try to pummel you the few seconds I have strength enough to.
For me, the rubbing of a finger's much different than a fingernail, or even a tickling finger. If my feet are massaged, I feel like I'm in heaven, but I did have to get used to some areas being rubbed, as my foot would jerk from them rubbing something in a 'ticklish' way. That is yet one more reason why the toes truly, and royally SU-U-U-UUUCCCKK!! And also why pedicures are just plain evil incarnate, sometimes. 😛issed