Personally, though, I think it's a combination of intelligence and sense of humor. You've gotta be someone, at the very least, that you can hold a semi-intelligent conversation with and is able to make you laugh.
I went out on a date recently with this guy and all he talked about was his workout routine, his muscles, and his cars. Any time I would try to change the subject, he would get back to one of those three topics. Seriously.
Thats not really the kind of conversation I want to be having. Give me some intelligence, please!!!
Another must is a sense of humor. I'm a sarcastic person...I need somebody who gets that - and can give it right back to me. Plus, they need to not take everything so seriously.