Argument from Authority: Because someone else has a PhD, your argument is invalid.
ad hominem: The argument put forth by that person you just quoted is invalid, because that person is; stupid, idiot, crazy, evil, dumb
Appeal to Tradition: You argument is invalid, because we've been doing it this way for a really long time.
Appeal to Belief: Your argument is invalid, because only a handful of people would agree with you; therefore I can dismiss anything you say
Appeal to Ignorance: Since it has never been tried before, we don't know that what you say is true, therefore your argument is invalid
Appeal to the Gun: Your argument is invalid, because people with guns will beat you, jail you or just shoot you, if you step out of line.
Appeal to Authority: You're argument is invalid, because you don't have appropriate credentials to make qualified statements on that subject
Red Herring: PersonG:"I'd like to talk about the ethics of the situation"; PersonH:"Yeah but ethics will never work in real life!"