There have been a lot of comments on this thread that armpits are easier to reach than feet. I'm not so sure. If you eliminate the shoe factor, things get a bit more equal, but even then, if you're having a tickle fight, legs are stronger than arms so you might have a better chance of being able to pull at least one arm up over her head (with your 2 hands) and hold it there with one hand while tickling her armpit with the other, whereas if she's kicking her feet all over the place you might not be able to catch and hold on to a foot as easily. If she's restrained properly, of course, the access factor is equalized. I like to tickle both, but there is a certain mystery about the underarm, even if she's wearing a sleeveless top, since basically it is unseen unless she raises her arm over her head which, in a typical day, would be a very small percentage of the time......thus a mystery. It is my impression, too, that generally the armpit is (slightly, at least) more ticklish than the feet.