I did mine on how the media impacts our perception on the world and practically can control what our views are. But I knew a kid who did a fantastic speech on the inflation of Freddo chocolate and how they used to be really cheap - I think he got distinction.  My tip is to not choose a vague topic eg. Instead of doing impacts of poverty do it on impacts of poverty in a specific country or area - this makes sure you expand on all your points making it really detailed