Ad Hominem (Argument To The Man):
attacking the person instead of attacking his argument.
Sometimes the attack is on the other person's intelligence. For example, "If you weren't so stupid you would have no problem seeing my point of view." Or, "Even you should understand my next point."
Oddly, the stupidity attack is sometimes reversed. For example, dismissing a comment with "Well, you're just smarter than the rest of us." (In Britain, that might be put as "too clever by half".) This is Dismissal By Differentness. It is related to Not Invented Here and Changing The Subject.
Ad Hominem is not fallacious if the attack goes to the credibility of the argument. For instance, the argument may depend on its presenter's claim that he's an expert. (That is, the Ad Hominem is undermining an Argument From Authority.) Trial judges allow this category of attacks.
Anticreationist debate tactics