I suggest a forum dedicated to debates. Throwing in your opinions and such on various topics, with mainly the same rules as the rest of the board but with certain rules rather harsh. The point would be mature debates, with no shouting or flaming, etc. and any (sensible) argument would be allowed.
I believe this should at least be a subforum, if added at all, because I don't really think debates properly fit into any existing forum without confusions and problems appearing.
I actually thought of this because I wanted to start a Religious Beliefs/Anti-religious beliefs thread.