The topic of censorship is appropriate as a persuasive essay topic -- one can formulate compelling and well-researched positions both for and against and for several contexts, including in school, on the Internet, on television, and in public political life. The topic can be prepared in different ways -- for instance, setting a limit on censorship or arguing whether it should be permitted at all, or even who gets to decide what is fit to pass and what is not.
What to do about climate change and other potential environmental threats is a strong topic for a competitive persuasive speech topic. For instance, the role of capitalism and the free market in determining solutions can be debated as can the degree to which certain countries -- such as the United States, France, Canada, and England -- should take a leadership role in developing new policies and technologies.
The topic of the legalization of "x" is a common and useful competitive persuasive speech topic given that the "x" in this equation can be filled in by a number of controversial variables: marijuana, prostitution, gambling or the consumption of alcohol -- in cases where one of these are prohibited. The topic is potentially vast since presenters can make legal, moral, or even economic arguments in favor of one position or another.
While it does not seem overly controversial to suggest that more healthy citizens is a good thing, the means, methods, and viability of better nutrition and overall fitness is itself in dispute. For instance, what role should the government play in the process? What about fad diets and the potential harm that they can cause? Should obese people or smokers be forced to pay more for health care or health insurance? This issue cuts deep into questions of individual responsibility and social well-being, lending itself to being an excellent competitive persuasive speech topic.