Start right in the spotlight

You've maybe heard many times that the first moments, the first 30 seconds or so, of a presentation are the most important. Not too conceptually difficult to grasp one might think. But the question is HOW do you get over that threshold. What exactly do you do with that gift of a chance to win the audiences total attention for however long you want to keep it?
I love openings, 'cos they're so important. Its easy to know what I might dare to do, but harder to judge on other people's behalf. My ideas tend to freak out some people!  So here are some ideas, some tips and maybe I'll put up more later. Promises, promises...
Easy ones:
Just jump right in there, no intro, no "thanks for inviting me", just get to the subject itself. Introduce yourself later on
Ask a rhetorical question
Describe a surprising, interesting statistic: "did you know that XX people die every year from...?"
Do a demo
Tell a story
Takes some thought:
Think of a metaphor that's very visual and will take you through your whole talk. Start with a striking photo and a question: "what do you think of this?", "what does this remind you of?", "have you seen one of these?" Gettit?
Build up a mystery, via a story
Takes some guts and skill:
Tell a joke (i.e. don't do this unless you're very good)
Go out into the audience and interact
Ask people to come up and help you with a demo