Anything allowed by the First Amendment, but subject to regulation at my discretion. Links are allowed, but do not post viruses, trojans, worms,etc. Rick rolling is allowed. Flaming and trolling are allowed up to a certain extent. If anything serious occurs, the offending party may be banned. Well, once I figure out how to anyway.
Oh and for those people who love to use the term "ad hominem", please learn to use it. A REAL ad hominem is when you're dodging the issue by attacking the person. An attack on a person, however, is NOT ad hominem. I've seen this with either legitimate comment posters or very amazing trolls. One thing that really pisses me off is when a person claims ad hominem when he is actually the person using ad hominem.