For me, the two biggies are appeal to authority and Tu quoque (best translated as Neener neener, you are another) Appeal to authority is acceptable where you show what the authority based their proof on, not on the fact the authority said something. Wrong appeals to authority are that a herd of people said the same thing, that because a person is an expert in X, therefore you should grant him the same authority on Y. Authorities are human, and subject to human responses. Too many folks use appeals to authority, so I tend to regard any appeal to authority with a whole lot of salt. Maybe an excessive amount. The other real bothersome one for me is just because a guy on my side is caught with his hands in the cookie jar, the guy on your side should get a pass for having his hands in the cookie jar before. Every act and actor is unique to itself, and excuses nothing. If it is wrong, it is universally wrong and makes no excuses for anyone. If B screws up his taxes, that only means that B screwed up his taxes. It is Even if B made fun of G for goofing up his taxes, it does not mean that B's problems are greater or G's problems are smaller. And it may just mean that taxes are too much for everyone and need to get simplified. It does not mean that B is wrong for having made fun of G. If it is wrong for someone to do something, it is wrong no matter who says so. And sometimes the person who is doing the same thing has good reason for making the assertion. A person who smokes 5 packs a day is perfectly ok telling someone else they shouldn't smoke because it is a vile expensive habit that is nearly impossible to break. They might even qualify as a valid authority.