I'm currently at uni, and an opener i've used more than a couple of times successfully, especially in clubs. Its untested in day-game, but i can't see why it wouldn't work.

Me: Hey, are you a cheerleader(s)?

THATS IT. The reason i find this is good is a couple of reasons.

Cheerleaders are stereotypically attractive, but also stereotypically bitchy/stuck up.

This means that if the girl(s) is not a cheerleader:
a) they take it as a compliment and go, 'oh no, im not, but thank you/ no i'm not, why do you think that?' or something along those lines. At which point i say 'Its just a shame so many attractive girls a stuck up/ You just had this look about you, do you think your more important than other girls?'. This can provide playful banter.

b) they take it as an insult they're usually very short with me: 'no i'm not, why would you think that?'. Then as they've taken the first comment as an IOD you can IOI by saying 'oh, you just have a really athletic build, you must workout'. This can act as a good talking point.

If they do happen to be a cheerleader then as far as i have encountered they will always take this as a compliment and say something like 'oh how did you know?' To which they are expecting the response 'your very attractive/gorgeous/athletic...' Depending on how they act, you can IOI them, but this is only if they show an instant interest in you. For example if they touch you when replying, or turn away from their group to directly face you. But for the most part i would say 'You just had this look about you... Do you think your more important than other girls?' If this is said with a cheeky smile then I often get a playful push, with the girl looking bashful and a 'no, of course not'. This is then easy to move into a talking point.

QUICK NOTE: Sometimes the girl will simply say 'no i'm/we're not, why did you think that?' in a very neutral way. To this I've used a mixture of IOI and dis qualifier. So something like 'You look like an active, athletic person/group, do you think your more important than other girls?'

I know i've used that past line a lot, but personally i love it, depending on the situation you can smile, and if there's a bit off natural attraction already (voluntary kino, lots of smiling, eye contact, etc.) it can be cheeky. Or if they are acting quite cold then saying it deadpan makes them start proving themself.

Hope this helps.