Bum
Although the bottom is much more acceptable in public viewing
(thongs, g-strings, and bare bums are easily seen daily on broadcast TV) than
the other intimate parts of the body, I have always felt that it is actually
a MORE sexual image in general. Perhaps it is because I have always
thought that the nude frontal torso rhymes visually with the face, and is to me
more closely tied to the personality. A well toned butt is highly sensual,
and it's functions are more specific, in ways that are generally not discussed
in "polite" conversation.