Lately I've been using the following with a lot of success :
Her: Why don't you give me your number, and I'll call you.
Me: Oh, come on (with a sarcastic smile in my face, that shows that I know what's going on), guys don't fall for that one anymore, do they?
OR
Me: That doesn't work anymore, does it?
Usually she'll laugh and either give in, or refuse, so I handle the objections by withdrawing the offer.
Me: Its ok, I don't need to get your number. (with an attitude of, 'its no big deal')
At this point, if they are interested, they'll turn it in.
If there is some intitial interest, it will work, if not, she'll just blow you off if you continue, and you'll sound like you're supplicating. Hot chicks are used to most guys crumblin' after the first objection, so its the easiest way to get rid of them; if they are interested, seems like they will still use that response to test you. Its worked for me several times in the last couple of weeks.