I was a student pilot, and I had forgotten or somehow never learned that CTAF at an uncontrolled field with an FSS on the field was always 123.6. I saw that UNICOM was 122.8, and so I figured that CTAF was the same. I took off on an intersecting runway, announcing all the while on 122.8, and nearly took out a Metroliner departing on the crossing runway (I was using the runway that the winds were favoring, they were using the longest available.) I was lucky that I didn't die or take out a bunch of innocent people with that stunt, and it took me a good 3 months to want to go near another airplane again. But I overcame my fears, finished up my Private, and progressed to where I am now. In a way, I'm glad that something like that happened to me--it's made me a lot more cautious and methodical throughout my flying career than I would have been otherwise.
But suffice to say, that was pretty dumb.
-Goose
P.S. Launchpad: I LOVE the avatar!