if the girl is hammered and doesn't want to have sex, it is rape, and that is taking advantage of a girl while she's intoxicated.
now. if this girl, is overly hammered, and wants to sleep with you, a few of the following statements are true :
she will likely puke before, during, or after sex.
she's a slut.
she might have a boyfriend. (who might be bigger than you, who might want to know where you live when she wakes up and asks you what happened and claims rape even though she forced herself on you)
you might wake up, and wonder what happened when your beer goggles run out.
one word - starfish
maybe she's really shy and wanted to get laid.
anyhow. please don't ever say taking advantage of a drunk girl, that's capitalizing on a situation. i personally can only really enjoy extremely drunk sex, when i'm drunk myself, because really, then you're fucking a train wreck and i can't imagine how that's fun. nor would i fuck a stranger at a bar. so.