The first is the ability to look for self-defeating flaws in arguments, particularly in regards to the exclusionary nature of truth. That is, if I hold that something is true and you believe in something contradictory, I must believe your concept is false. There is no such thing as, "This is the truth for me." After all, if there is no such thing as universal truth, then "this is the truth for me, but not for you" cannot be universally true. Relativism dies from self-inflicted wounds. I'd seen this trick before, but never described so succinctly and clearly.
Another good example is the assertion that support for gay marriage is open-minded. It is not. Muslims, for example, do not support gay marriage. If you hold that gay marriage should be legal, then you must assert that Islam's teachings on homosexuality are wrong. There are no two ways about it. You aren't being open-minded at all. You are affirming a very distinct position and denying all contradictory ones. "Love wins and the rest of you morons lose" ought to be the gay marriage slogan.
Bonus tidbit: David Hume's foundational statement for skepticism is taken out behind the barn and shot quite nicely. Here's what that sounded like as Normal Geisler shot it in front of his college professor.
"The principle of empirical verifiability states that there are only two kinds of meaningful propositions: 1) those that are true by definition and 2) those that are empirically verifiable. Since the principle of empirical verifiability itself is neither true by definition nor empirically verifiable, it cannot be meaningful."Ouch. That had to hurt.