Let me put it this way…I look good in red, but I look better in nothin’. I feel sexiest in the buff.
But if I have to pick from the list, I’ll go with short skirt and heels. I’ve got a great ass and pretty good legs, so I like to show those off.
I feel sexiest on date nights. Usually it’s just jeans, kitten heels, and a nice top, but I make an extra effort to wear more make up than usual (meaning more than none, but still natural looking) and spend extra time on my hair. I most often let it curl on date night. My favorite top is white eyelet with a scooped neckline.
Basically, it’s not the outfit, it’s the time spent in looking my best. When I get dressed up, dh notices and his attention is what makes me feel the sexiest of all.
…the powerful embrace of a wonderful lover who is kissing and holding me expertly and passionately.
I feel sexiest in what the man on the street doesn’t see – great lingerie. In my younger years, I mostly went without, and then graduated to utilitarian. But now that I am of a certain age, I’ve discovered the very great pleasure of beautiful, properly fitting bras and panties. Secret, sensual bliss.
On a more mundane level, I feel confident and terrific in jeans and boots. Reversing the question, the sight of a pair of well-worn Frye boots on a guy (with good butt and thighs) in well-worn jeans makes me instantly hot. I mean, instantly.
No votes for over-sized sports jerseys yet? I bought my last LTR a big Boston Bruins one for her to wear sometimes just lounging around.
It burninated the hotness scale and she knew it when she wore it.
I’d have to say loose-cut jeans, hiking boots and a sports bra. I think my honey would agree. I’m not trying to please any guys, though, so that might skew the results a little.
Mmm… sports jerseys…
The two sexiest women I’ve ever seen have both wore these. One of them was my wife, who will from time to time steal my old football jersey (black with red/white lettering) and wear that. If she’s feeling especially nice, she’ll tie it off in a knot, but either way, rowr!
I realize that I may be biased when it comes to my wife being sexy, but considering how many offers she gets at the bars, I think I’m justified in declaring her hotness. 
The other was a dancer at one of the local strip clubs. She’s the only woman I’ve ever paid to dance for me, and it was the jersey that did the trick. Fortunately she had (or could at least portray) intelligence as well, and we chatted for quite a bit before she went back to work.
Considering that I don’t even like sports, I have no idea why the jerseys make the cut. But, damn.
And, to answer the OP: as I’ve said before on this board and elsewhere, I find glasses to be the hottest fashion accessory a woman could wear. Not shades or sunglasses or Paris Hilton boogy-eyes, but ordinary glasses.
Combine those with a nice skirt or tight jeans and a well-cut sweater or button-top shirt and I’m a drooling caveman.
Pardon me, I need to be alone for a while now.
Having spent about a month so far at a military base populated by all four branches of the US Armed Forces (not counting the Coast Guard), I’ve gotta say “Navy Service Whites”.
In general though, I’m a fan of tight jeans, boots, and cowboy hats. Really any kind of shirt will work with that setup.
Also, a ditto for Star Trek TOS uniform.
I feel sexiest when I’m naked.
Seriously. Clothes never really appealed to me, they don’t usually flatter my body shape (curvy hips, big tits.) About two seconds after I come through that front door, off go the pants. My husband has taken to calling me ‘‘O Pantless One.’’
I spend a lot of time, even just lounging around, not wearing clothes. It just makes life easier, and greatly increases the odds of me getting a back rub.
And with sex, I know how to wear naked. I know how to accentuate the strengths of my nakedness, in the same way another woman might know to wear heels to accentuate her sexy legs. It’s my favorite fashion accessory!
ETA: Oh, and evening gowns. The more romantic and silky and elegant, the better. The process of going from a complex network of evening wear TO wearing nothing but skin is the seeeexiest thing EVER.