First let me start by saying that I hate using other people's canned lines. I prefer sourcing a genuine observation. But I'm a quick thinker, so it works for me.

I love this one.
If you're on the second floor of a bar, find a girl standing by the rail(over the dance floor, stairs, awning, etc).
Right up to her ear, so it seems like a secret:

"I know what you're thinking. But DON'T spit over the rail."

90% of the time I get at least a good laugh out of her. She'll usually want to start a conversation w/ me after. You can take it wherever you want from there, but it's an easy ice breaker, and it doesn't sound like a tired line.
There are other variations, like "I'll give you a dollar to spit into the crowd." But watch out, I had a couple girls do it. Gross.

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Live your life, as if your life depends on it.

LOL, those are good, I'll have to keep those in mind for the next time I'm out.

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Been around the world twice, Talked to everyone once...