Are you looking specifically for a famous persuasive speech, or are you required to write a persuasive speech? I recommend you look at a speech database and choose a subject/speaker that you find interesting. The speeches given by presidents and leaders of the nation reflect a wide range of persuasive topics: inaugural speeches, call for action during civil rights era, war-time speeches etc.
Now if you are looking to write a persuasive speech, there are a variety of rhetorical devices and formats you would want to follow. Most persuasive speeches will follow the basic: claim (argument), problem and blame (who created the problem) and some call to action (solve the problem). Your determination of the audience will determine the type of appeals you incorporate into your writing: ethos, pathos, logos.