The most satisfying has to be Mosley over Vargas, although I my heart hurt for Vargas. Mosley WILL be the first man to beat Mayweather. Ahem... sorry... That was a TKO anyway.
I have to agree with "The Game" on this one. Ponce de Leon knocking out that poor guy was the most unreal knockouts I've seen in a long time. And that is a was a pure knockout to the tenth power. That dude was OOOOOUT!