Here's a specific one I used last weekend at a regular house/apartment party.
I had been there about 10 minutes just talking to the 5-6 people I already knew and there was music playing so I just kind of bounced/danced over to an HB 9 and said "I haven't met you yet!" and she was really receptive to me (I've used this one quite a few times in party environments and it has worked every time, just remember to keep the energy up) Then as I was shaking her hand I said "Well as long as we're talking, I might as well spin you or something since the music is playing!" (Keep in mind she was already semi-dancing but more interacting with some other people just kind of floating, so I wasn't getting sucked into the "dance floor trap") We then danced for a few secs just kind of flirting...
She was immediately interactive with me and I stacked to another situational opener that I made up on the fly. She had what I like to call "short flippy hair" and I mentioned that she should have some knee-high, white go-go boots to go with her hair. (a very PLAYFUL neg) and she immediately started shooting IOI's all over the place. I then kind of transitioned into my personal "Generational/Decade Selection" routine.
I know this went beyond the opener you asked for but the key is that it's OK to be situational at parties and such as long as it LEADS toward more attraction/comfort and not just killing time with boring stuff like "So, who do you know here?" The action is fast paced so you can usually blaze through A1-A3 pretty quickly and get into comfort. As always, pre select your C1 isolation area ahead of time so you can bounce within the venue (In this case it was an indoor party so mine was to the outside balcony...it was chilly out so you can guess who got cold and who did the warming up
) Happy Hunting Comrades!