A logical fallacy is a flaw in logical reasoning. There are numerous flaws in judgment. One example is the "ad hominem" fallacy, where instead of arguing a point, the person attacks the person's character. Ex. "We should ban cigarettes." "Why should I agree with you? You smell really bad!"
Another example is the "burden of proof" fallacy, where a person who makes a claim states that it is up to the other party to disprove them, rather than prove their own statement. This is fallacious because the inability to disprove something doesn't automatically mean that it is proven. Ex. "There is a teapot floating in between Mars and Earth at this very moment. Prove me wrong!" "I can't do that, because I can't go to space right now." "Therefore, I am right!"