"Thats a really nice outfit you're wearing. It's gonna look even better balled up on the floor at the foot of my bed in the morning."
I've used that one periodically and with pretty decent success. It's all about the delivery. Pulled it on a few girls that were way outta my league and weren't even giving me the time of day. If said with just the right amount of confidence and humor its an absolute home run because its so over the top. But if you're off just a little, you are the biggest creep in the bar
"hi, can you dance?"
when they decline:
"no, no... i wasnt asking if you wanted to, i was asking if you knew how"
This one is surprisingly effective as well. A lot of girls will get up just to show you they can. And THAT my friend is all you need.
And then there are the classic lines that play on extreme shock followed by extremely disarming humor, for instance:
"Hi, you are really freaking sexy. Want to go back to my place for some pizza and sex?"
Once you recieve a horrified look of fright follow with this one...
"What? You dont like pizza?"