Armpits
Among all the tickle people, it has always seemed to me that the majority prefer tickling feet. I suspect that a sizeable percentage of these are also foot fetishists.
I don't think I am a fetishist of any part of anyone's anatomy, but I surely am attracted to female armpits, and I DO have an intense tickle fetish. I generally prefer upper body tickling. I have always considered myself lucky that my better half is more ticklish in the armpits that almost anywhere else, at least tied with the area up between her legs.
Like Mia, I am quite attracted to the scent, and I also have read about the hormonal aspect of that region. Who knows, maybe that's why I like armpits so much, although I enjoyed the tickling of my aunts' armpits, and my female cousins when I was still too young to notice anything hormonal or whatever.
Although she doesn't share my tickle fetish, my wife does know about it. She let's me tickle her although she fights it like crazy when I start. She also exploits my love of tickling and my attraction to armpits. Many times over the years she has stretched her arms over her head, and has glanced at me to make sure I am getting the full tease. I actually think she might be a little disappointed if I started failing to notice...which hasn't happened yet.
There is one last part of this. Armpits are made to be tickled. You can do it with one finger, two, finger and thumb or all fingers. If you hold a woman's arms over her head with her wrists crossed, her armpits literally twist toward her front and invite your fingers like neon signs.
Finally, there is a part to the teasing aspect. Despite her laughing, my wife screams as much as she can that I'm making her mad when I tickle her armpits. When I do this in bed at night, she goes just crazy. Then when I let her go, she often tries to give me the "cold shoulder" turning away to face the far wall. After a proper amount of time, though, she reaches down behind her to search out my person. Even after all these years she still starts to giggle when she finds that I have stiffened my resolve, if you get my meaning (I think I do). That often leads to the next part of the tickle session, and the start of a beautiful night.
Armpits are the best...no doubt about it.
Hiram