I look for a guy who is confident in who he is, both physically and intellectually. For physical traits, I'd like him to be tall, which I would considering 6' and above), muscular, but not so muscular that that's all he thinks about. Well groomed, but again, not to the point where that's what he worries about all the time.
He's got to be a good conversationalist, always has something interesting to talk about. Intelligent, not really an expert on everything, but knows something about many different things. Caring about what is going on in the world, whether it's animal cruelty or politics or the war in Iraq, etc. He's got to be able to stand up for what he believes in. On the same note, a guy who's not afraid to stand up to me when he thinks I'm wrong. I don't want a guy who's afraid to argue with me when it's something important to him.
I think from the answers already given you can see that confidence is the #1. Becca is right. There has to be a balance between confidence and cocky. There is nothing sexier than a respectful confidant man. I love a man who isn't afraid of being socially intimate with me. I hate when men don't want to be that way with me because they don't want to look stupid around the other guys.
Physically I love a man with cut tan forearms! Another big turn on is good hygiene. Fresh breath is awesome :)