While I'll admit I can be rather versatile as the situation warrants...
...and based on the ticklishness and/or desires of the 'lee, I WILL freely admit that I'm a foot man. Nothin' wrong with that, though I will admit it's maybe more common than most 'lees that prefer upper body and other such tickling would like. But again, I'm a versatile fellow and, not taking the 'lee's hot spots and likes into account just for the sake of me coming up with my own list, here goes:
1) the bottom of the bare foot
2) the bare toes
3) the tops and sides of the bare foot
4) the belly
5) the navel
6) the ribs/sides
7) the underarms
8) the hips
9) the neck
10) the knees
11) anywhere else that would work pretty well
See? Versatile. If a lady 'lee isn't particularly into feet all that much, I adjust accordingly. After all, if she's not having fun, then neither am I, but this WAS a list that asked the 'ler's preferences, so in an ideal world, there it'd be. Great thread!