Keira Knightley
Katie Holmes
Straight female.
I find Michelle Pfeiffer hot, and I’ve always admired Katharine Hepburn.
Straight celibent female here.
The two woman I find the most attractive are Jenna Elfman and Jeri Ryan. I’d go nuts seeing the two together.
On the male side, I love Tim Curry and ET reporter Steve Cojo-whatever. Only he’s openly gay. The main guy on my list, and probably the only man I would give it up for is Montel Williams. He is drop-dead gorgeous!
Angelina Jolie! Angelina Jolie! Angelina Jolie! It’s a good thing that she and Billy Bob Thornton adopted a child–a biological child of theirs would be so hot that he could have his own solar system. (Or the kid would be remarkably ugly. It could could go either way with those two.)
I also find Catherine Zeta-Jones incredibly beautiful. I remember when she was first becoming really famous and was on a lot of magazine covers–I’d just stand in the supermarket staring at her face on the magazine rack. Then, I read a discussion of her at another message board, where the people there seemed to think she wasn’t anything special. That really surprised me. This thread makes me feel better, though!
I also find Soledad O’Brien (morning anchor at CNN) very attractive. I love her combination of looks and personality–and she’s a great newsperson too.
Others that people have mentioned in this thread that I think are very attractive: Halle Berry, Salma Hayek, Tina Fey, Queen Latifah, Missy Elliott. I guess I like dark haired dark-eyed women. Not surprising–I have a strong preference for men with that coloring.
Benicio Del Toro: Holy shit yes!
Sean Penn: I don’t find him attractive in the least.
Bisexual male checking in.
My wife and I’ve compared notes and we’re generally attracted to the same types of people:
Male
George Clooney
Oded Fehr
Jason Statham
Female
Salma Hayek
Daisy Fuentes
younger Sophia Loren
I thought Gina Gershon and Jennifer Tilly in Bound were extremely hot.
Looks? Probably Colin Farrell (probably because I look like him but never quite as good, I always thought I could look better if I just got spikes that looked like his) and Brad Pitt from Fight Club.
Personality? Without a question George Clooney and Brad Pitt in Ocean’s Eleven, it’s without a doubt the personality I strive for, especially Clooney’s.
Straight male.
Johnny Depp for sure. Viggo Mortensen when he’s got the Aragorn wig; I think he loses it a bit with shorter hair. Redford before he got left out in the rain. And McCartney. He’s getting a bit jowly and turkey-necked, but somehow he’s even more interesting looking than when he was young.
Straight male.
Sean Bean. Particularly as he looked in the “Sharpe” series.
I was waiting for somebody to mention Sean Bean.
He is just so effing hot.
Yup, I think so. I’d mortgage my non-essential internal organs to be as hot as he.
David Boreanaz
Orlando Bloom
I wish I had Colin Farell’s body although with his head he looks apeish
Het female checking in.
I have always had that thing for Catherine Deneuve. And another thing for Susan Sarandon. Needless to say, I enjoyed The Hunger a great deal!
Man, I gotta get my SO over here and rent that one!
I’d have to go with Keira K and Scarlett J. (If I just use initials I don’t have it spell it 
.
I especially love Keira’s voice.
Oh, straight female.
Still straight, still female.
I forgot to mention not overly well known actress Azura Skye. She played Cassie who quite correctly foresaw her own demise and some other stuff as well in Buffy. I was reminded of her because she had a part in The Handler the other week. She has so much charisma and seems such a cool person. A bit like an indie Drew Barrymore.
Straight male here.
Just for the record, I think Pamela Anderson is the most repulsive-looking female celebrity out there. Yuk. I hate that look. She looked wonderful when she made her first appearances in Playboy - she looked natural and unenhanced. Now - gag.
What male celeb would I like to look like? Michael Dorn (Worf on Star Trek: TNG). I’m not the right race, but so what. He’s an attractive man.
And based on the comments I’ve heard from many of my female acquaintances, I’ve decided that looking like Orlando Bloom as Legolas would be a really good thing.
Sorry - Gina and Jennifer were mine, not Hamish’s.
Straight female here.
Madge Sinclair was a beautiful woman. Those cheekbones and voice, and the way she carried herself. Damn, I hate leukemia.
Catherine Zeta-Jones. It’s the eyes and the hair.
My paternal grandmother. I saw a portrait of her when she was eighteen or so. High cheekbones(I have a thing about them), dark eyes, hair swept up in a pompador, she looked a little like Sophia Loren.
Straight Male.
Elijah Wood.
It even sounds like “I would,” if you’re drunk enough. 
I’ve also mentioned before that I’d want to look like Ewan McGregor. I think Jude Law is slightly better looking, and I personally find Jonathan Rhys-Meyers more attractive, but I’d still prefer to resemble Ewan.