I think the best openers have a slightly patronizing edge to establish your position as alpha male and either asks the girl to do something for you (puts 'em to work) or baits the girl into qualifying herself. Lets make a list of openers that can accomplish these things:

Hey you look fun. What do you do for fun around here? (credit: DevonAero)

Hey, you look fun. Are you?

Tell me, are you as interesting as you look? (credit: WetDreamAmnesia)

Are you looking to meet people here? (follow up questions can be how she came into the position of being single)

Hey, you look like the adventurous type. Lots of people say they are adventurous, but few of them really are. (credit: ThrowawayPUA)

You're beautiful, but so are a lot of girls. Are you more than a pretty face? (credit: birdwontquit)

The following openers need a task or qualifier- question to make them complete: Point at girl repeatedly and say "you", "you", "you"..."I think I know you!" in energetic and funny manner. Pull girls in..."I don't really know either of you but I wanted to talk because you're cute." (Credit: Bong-water)

Hi! (wait for return hi) My friends call me_____. What's your name? (credit: amnislupus)