So I'm sitting at the bar when all of a sudden a cute girl walks directly up to me and she brushes up against me (proximity). What would be a good opener? P.S. she was away from her friends.

tbh - any direct opener...
1. -I want to find out if there was more to you than meets the eye
2. -You look like someone I'd like to meet
3. Very simple -Hi! How are you?

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Knowledge is power, guard it well.

the trick to direct, is when you are direct you are honest with intentions, has nothing to do with canned openers, it is an expression of your desires and how you truly feel, walk up, make eye contact, say hi, drop a preframe, like this might seem weird, this might sound strange, or you probably get this all the time, or please don't be nervous but...

and then reveal your intentions/desires in a direct manner, just be 100% honest and genuine and say exactly what is on your mind, if you are nervous just say, you really make me nervous, if you think she is cute, say you are cute, if she is making you horny, you really make me horny, just say exactly what you are thinking and be genuine about it and congruent, don't take it back, don't appollogise, do not do this to impress her, do it to express yourself

"Oh hey there! How's it going?"

It doesn't have to be direct either. I'm usually more "casually friendly" when I do it. Like I'm just being social and saying hi to her because we're stuck at the bar together.

If she's alone just standing somewhere:

Me: "what's up? got no friends?"
Her: "Umm I have friends, I'm just waiting for them"
Me: "Sure you are toots. It's ok you don't have to lie to me... I'll pretend to be your friend for a while"