Chocolate Ice-Cream Cake!
As the Ler in a particular S&M relationship, your Lee is fond of a teeny bit of pain spiking the tickling pleasure.
If you're going to have the privelege of tickle-torturing them into squirming, giggling fits of orgasiatic delight, you'd better be ready to either:
a)apply a bare-handed spanking to their bottom
~or~
b)occasionally bite them fairly hard on their nipples and neck
...or they'll be rather pissed-off.
Since it'd make them(and possibly you) happy, which option would you inflict/provide for their overall enjoyment?