Burden Of Proof Fallacy:
the claim that whatever has not yet been proved false must be true (or vice versa). Essentially the arguer claims that he should win by default if his opponent can't make a strong enough case. There may be two problems here. First, the arguer claims priority - but why is it him who wins by default? And second, he is impatient with ambiguity, and wants a final answer right away. A counter-argument is the phrase "absence of evidence is not evidence of absence."
Argument By Question:
asking your opponent a question which does not have a snappy answer. (Or anyway, no snappy answer that the audience has the background to understand.) Your opponent has a choice: he can look weak or he can look long-winded. For example, "How can scientists expect us to believe that anything as complex as a single living cell could have arisen as a result of random natural processes?" Actually, pretty well any question has this effect to some extent. It usually takes longer to answer a question than ask it. Variants are the rhetorical question, and the loaded question, such as "Have you stopped beating your wife?"