I'm usually not big on canned openers but I've used this one several times and the girls pretty much always laugh. It's a great ice breaker, and is even better for girls in groups.

Sometimes girls will be standing or sitting around, looking bored, and with their phones out. If all or most of the girls have their eyes glued to their phones (and are probably texting someone), I just nonchalantly walk up and "join" their little circle, whip out my phone, and start pretending to text with them. Then we look like a bunch of nerds playing our Nintendo DS's.

This one is fun because you don't even have to say a word. You're just lightly busting their balls for having their eyes glued to their phones, without being a dick about it. The girls will pretty much always laugh. Some girls have even said stuff like "haha yeah you're right I am kinda using my phone too much. How's your night going?"

Boom, you've broken the ice and can easily move on to introducing yourself and getting her name.