Interesting question - but I don't think there is a single body part that someone doesn't find sexy. Unless you're talking internal - I mean I rarely find myself saying 'My, my - what a wonderfully sexy spleen he has' - 'Hey, check out the pancreas on her! Woah yeah!'
Nah - but seriously - on guys:
Adam's apple - I love watching them bob up and down when a guy is talking, I love kissing them, biting them (gently) and running my thumb softly over them.
Thighs - thighs and the places they lead - no, not knees, other direction
Scars - especially on tanned guys
On girls:
The backs of their knees - licking them and tickling them
Ears - sorry guys women have sexy ears, men don't - dunno why (I don't dislike men's ears, but they aren't sexy)
Noses - but only if she know how to use it :wink: