@baum - I don't know off the top of my head; I'll get back to you after I do a bit of research
@ava - why would you want a 'badass' way to reject her; to show off? While that may get the yucks from your buddies, showing a little class is more likely to get a favorable reaction from other members of the opposite sex, including some you may find neither unattractive nor uninteresting.
In any case, if she hasn't come out and said anything directly, playing oblivious is a great way to go. She'll eventually give up in frustration, and without giving her a specific *reason* for rejection, she doesn't have anything to argue against (ie: "I only like people with X quality" "I have X quality / can work on it if you give me a chance")
Another idea is to express interest in someone else, which would indicate you're not on the market. The risk there, of course, is just like telling Russia you plan to Sealion England, word can get around, with various negative consequences if you *aren't* actually interested.
Your final option is the most brutal: bluntly indicate a lack of interest. It's not a pleasant thing to experience, so there isn't any need to be 'badass' to ruin someone's day - but unfortunately, sometimes its the only option available.
Well, you could also take a six month job on the other end of the country. Works great for leaving drama behind ;)