Politics is a popular topic for argumentative research papers, because politics is by its very nature a topic of debate. Politics is also a diverse field, encompassing such topics as policy, political parties, elections and international relations. An argumentative research paper on politics can deal with any of of these topics. For example, an argumentative research papers on U.S. politics can argue for or against reforming the two-party political system. A topic for a research paper on European politics can argue for or against the idea of Europe integrating militarily.
Economics is frequently a heated debate topic. Academic economics is divided into several competing camps, many of which correspond fairly well to political ideologies (e.g. Keynesianism and social democracy). Because economic arguments are so contentious, they make excellent topics for argumentative research papers. One topic for an economic research paper is the Keynesian-versus-Monetarist debate. Keynesians argue that governments should spend money to spur economic development, whereas monetarists argue that interest rates and other financial policies spur development. An argumentative paper would pick a side and argue for it.
Social issues can be hard to define, so much so that there is sometimes even debate over what is or isn't a social issue. Social issues topics include abortion, drugs, stem cell research, poverty and demographics. Take the issue of drugs, for example. An argumentative paper on drug policy argues for or against one of the possible ways of dealing with drug problems in society. In fact, you could even argue about whether society is facing a drug problem at all. The only requirement is that the argument be backed up by facts.
Scientific findings are not off limits for debate and discussion. In fact, scientists debate their own research findings all the time, in scientific journals and at academic conferences. Topics for argumentative research papers in the sciences include biology, psychology and neuroscience; topics like chemistry and physics do not lend themselves as well to verbal argument. For example, in neuroscience, you could write a paper arguing for or against a neurological basis for consciousness, drawing on brain-scan images and other pieces of evidence. Such a paper would draw on evidence from biology or psychology to strengthen the case.