Probably hearing about the 9/11 attacks on TV on, well, 9/11.
It didn't impact my current world view much because I would've learned that there are far too many Crystal Light noses (haven't used that term for jerks in awhile, have I?) in the world anyway. And also because, at the time, I was incapable of having an opinion on politics that made any sense. (I mean, where the sail would I have gotten one of the invincibility stars from Mario to kill the terrorists with? [The fact that I thought I wanted to kill them at all is also a part of how stupid I was back then, by the way. Good thing I only thought about that idea...])