The Great Debate: Is meth really that bad?
But yeah, if you're teacher is chill and will actually grade you on the use of arguments more so than how much he agrees with the topic, then go for something funny that you and your class will find interesting. It'll be so much easier to retain and make it fun to do.
You can argue the merits of beer over water, or maybe something to do with polygamy. The world is your oyster.