For women
The eyes - regardless of the color, if they have that lusty sultry look, I melt every time.
The Hair - For the people who have talked to me know that I of all people, love women with great hair.
The Stomach - A toned stomach is truly wondrous on a woman
The thighs/hips - I LOVE well developed thighs on a women because I love a girl who is strong and confident. Full hips are always a plus as well. Additionally, most women who have rocking thighs tend to have a pretty nice butt as well.
Lastly a woman's eyebrows and eyelashes really go along way to finishing a stunning feminine look.
This being said, being proportional is key to the overall aesthetic
For Men
The jawline - Not too sharp but well defined, this is a defining feature of a man.
Arms - Another key feature of masculinity, some people are more slender and lean and still others have barrel chests and pectorals of a bear, but well defined arms are a hallmark of all strong men.
Quads and forearms - This one is a little out of the ordinary but well defined forearms and quads sre just awesome.