Others:
“Is this your first time here?”
“Have you ever heard this fellow/woman speak before?”
“I don’t think we’ve ever met. I’m Rae. Ray of sunshine!” also good for a laugh … sometimes.
“Gee, this weather sure sucks!”
I’m not so sure the conversational opener is the most important part. Perhaps the follow-up question to whatever their response is more important. You would want to go with an open-ended follow-up question to get them talking.

In my book Power Networking for Shy People: Tips & Techniques for Moving from Shy to Sly! I describe having a Questions Toolbox. The idea is that you prepare in advance for questions that can move a conversation forward. It also prepares you for questions that you don’t want to answer.
Most people like to talk about themselves and their business. And they can easily resonate with you if you are a good listener.
I enjoy a good conversation. Even though my default mode is a shy, introvert, I’m far more outgoing than most people. I find that if I take the lead in the conversation it usually goes well, as I have training in communications.
Thanks for your question.
Originally answered on Quora.com