If you want a challenge (as well as a gold star sticker from your teacher), try a touchy subject. Fatty food, violent video games, cigarettes... Another possibility is to try something where the target audience isn't obvious, like TVs (broad audience) or panflutes (narrow audience).

Of course, if you just want it to be easy so you can be done with it, do the opposite of the above. Something few people has a problem with and where the target audience is clear from the start, like toys or razors or what have you.