Women's feet can be very sexy.
Here's what does it for me:
Beautiful, well maintained sexy feet. Nice high arches. All 5 toes the perfect length from shortest to longest.
Also, the curve of the female foot is shapely similar to a woman's body which triggers a state of arousal in some men. I love when my wife takes her nylon pedicured feet out of her leather heels after a long day and lets me rub, kiss, and smell them. The pheremones given off by (some) female feet is very arousing. Just perfect!