Flawless skin, I mean, I hung out with my ex crush yesterday just to answer this question.
He has a perfect teeth indeed but he's 18 and his skin looks like a 30 years old one, so damaged, full of pimples and just dry and creep because of smoking and bad care, not just an hormonal thing.
So... Flawless skin, I have one at the height of puberty. But I would kill to have Miss B. Spears flawless smile.
A guy's smile is one of the first things I look at and one the most important factors I have in finding a guy attractive. Nice skin is also important, but I think I'd give teeth prominence.
but he's 18 and his skin looks like a 30 years old one, so damaged, full of pimples and just dry and creep because of smoking and bad care, not just an hormonal thing. 
But I would kill to have Miss B. Spears flawless smile. 