Coming up with a really good persuasive speech topic can be a bit of a challenge. Your topic has to play on the emotions of your audience, ideally by touching a nerve that stirs them to side emotionally with your point of view. Finding topics like these is not difficult. You just need to have an inquiring mind and pay attention to topics that already are reaching people on an intensely emotional level.
Although they can be extremely controversial, religious topics make for good persuasive speech topics. In fact, the controversial nature of religious topics is precisely what makes them effective for persuasive speechmaking. Most religious topics have an overtly moral or ethic bias towards one perspective on a particular issue. For instance, you can argue the issue of whether abortion should be legal from a moral religious point of view. The same is true regarding the legalisation of homosexual marriage. The intersection of science and religion can also be a fruitful area for persuasive religious topics. You can argue for or against cloning, or stem cell research from a moral perspective; you also can speak on capital punishment in this same vein.
Another way to stir the emotions of a crowd is to hit them with a persuasive speech concerning a controversial legal issue. For instance, ongoing debate over global warming and climate change could provide you with enough fodder for a speech on laws that could and maybe should be passed to regulate companies to limit their impact on the environment. Whether assisted suicide should be legalised can make another good topic. This one also works from a moral standpoint. A third possibility might be to speak on how to deal with immigration policy and whether illegals should be deported.
Issues regarding health can form another pool of topics for your persuasive speech. Look for topics that tend to polarise many people. For example, a speech on why people should be vegetarians is likely to be effective if you provide scientific data that vegetarianism has many health benefits, rather than simply focusing on the idea that killing animals for food is wrong. Another possible health topic that has legal implications is the benefits of having or not having universal health-care coverage. Whether cosmetic surgery is good or harmful for the human body might be a third health-related topic. The possibilities for health topics are limited only by your own imagination and ability to choose a topic that prompts people to react with feeling.