First Principles:

1. The burden of proof rests with the person making the assertion.
2. Extraordinary claims require extraordinary proof.
3. It is nearly impossible to prove a negative; for example, that unicorns don't exist.
4. It's easy to make an assertion. It takes time and effort to refute one.
5. Correlation doesn't imply causation, "anecdote" is not the singular of "evidence", "this actually happened to a friend of a friend" is not statistically significant, and an ad hominem argument speaks to the person making the argument, not to the argument he or she is making.
6. That said, correlation can indicate causation, anecdotes may constitute evidence, and an ad hominem argument can be a legitimate response -- depending on how they're used.
7. There is no consistently reliable substitute for knowing how to construct an argument.
8. Logic and argumentation test propositions. They don't conduct original research. A badly made argument can assert a point of fact which turns out to be true, and a well-made argument can be made in support of a point which turns out to be incorrect. Note: pointing this out does not constitute a refutation.
9. Having a phrase become a popular comeback in internet arguments doesn't make it invalid. It just makes it irritating.
10. It's more important to be right than to have authoritative credentials, but generally speaking, credentials and experience matter.
11. If you think it's more important to win an argument than to arrive at a valid conclusion, you are a n00b. If you can't tell the difference between winning an argument and having the other participants give up and go away, you are likewise a n00b.

Offenses against reason and evidence violate one or more of these principles. Some examples:

  • Oh, yeah? I challenge you to prove me wrong.
  • I am an expert on this subject! Submit now! Resistance is futile!
  • Sorry I couldn't look up every little detail about {easily found facts that would have undermined the speaker's position}. Some of us have this thing called a life.
  • As far as I'm concerned, not a single one of your points has been proven. (Said after one's opponents have documented and logically demonstrated every one of their arguments.)
  • Generally, one is required to refute a point before claiming it is incorrect. You have yet to do so - as you cannot - so it still stands. (An alternate version of the previous maneuver.)
  • You can't handle the truth! (Quote from the film A Few Good Men (1992, dir. Rob Reiner), delivered by Colonel Jessep (Jack Nicholson).)
  • How can you say the data supports you, when I have a personal anecdote of the exact opposite thing happening?!? (Used on any topic that involves data or statistics.)
Why do you say that a safety recommendation is safe? I have a personal anecdote of someone dying, so how can it be safe?
I've done the unsafe thing all my life and I'm still alive, so there!

Most of the material in this wiki could be shoehorned into this one category, but it's more useful to classify items by their other characteristics.