Happiest moment: When Robert Namo discovered the QGN (No!) voice command for the first time (that I, he, and many others have seen by now, but which was news to everyone at the time; this was very soon after it was added, I guess) on his character, Iraqi Namo. My memory is blurry, yet the important details remain.
-It was near round end. Robert's team was ahead quite a few players and were just hunting down stragglers at that point.
-Iraqi Namo suddenly says "No!" while running, stops in her tracks, and spams it repeatedly (this was before flood).
"No! No! No! No! No! No! No! No! No! No! No! No! No! No!"
The character of Iraqi completely snapped and rejected everything that was going on around her until the next round began. Something about how this all transpired, coupled with my own lack of sleep, made it one of the most hilarious and memorable moments I've witnessed in cRPG.