I wholeheartedly agree with this one:
Nape of neck
The neck is so sensitive that even the slightest touch can turn on your loins, which makes sense—as White notes, the inner thighs, back of thighs, the nape of the neck, and even the arches of the feet, “all bridge a connection to the sexual center and are great areas to focus on beyond the genitals.” One way to explore the neck is moving your fingers along it or softly blowing and kissing it.
Or licking it...