A good, thought provoking speech.

However, honestly, it's just as much about the way you present the speech as it is about the speech. Do it confidently, don't 'uhm', 'ahh', or the like, and speak sloooowly. Seriously on that last one, too, you'll feel like you're speaking at a snails pace, but everyone will think you're speaking normally. (At least, that's what I know, from my limited public speaking experience)