You should look for something that interests you. That is the only way to really enjoy writing a research paper. We cannot really help you know what interests you, especially since we do not know where you live or what class you are writing this paper for. You could literally write on any topic in the entire world ranging from "Should Japan stop using so much nuclear energy?" to "How and why did the Norteno style of music become popular in northern Mexico?" Anything that interests you is fair game as long as it's related to they class you're taking.
The best topic for any essay is one you are interested in. Try brainstorming a list of topics that interest you and are within the parameters set by your teacher. Take this list to your library or other resource center and see how much information is available on the topics. If you have a topic that only returns one or two books, you might want to cross it off your list. Once you have narrowed your list to things that interest you and have plenty of reference material, select the one you like the best or the one that you think will be the easiest to write about. Remember, if this is a research project, you will likely be working on it for a while so make sure you are truly interested in the topic.