My old roommate and I used to stomp on hightower. We both play soldier, so we would rocket jump around and just try hard being obnoxious in voice chat.
One such game we were playing, being assholes when I caught sight of two players by the tower trying to stand on top of each other. So I stood there to watch for a little bit, and eventually my roommate joined me. Soon enough a couple other people came in and eventually we started all switching to soldier, and trying to stack each other as high as we could. After maybe 20 minutes of grueling effort, we finally managed to stack everyone in the server in a giant tower. It was truly majestic.
We all sat there quietly, for maybe 10 to 15 seconds all admiring the majesty we had created.
Then I heard my roommate laughing hysterically from the other room, and a little above me I saw his character model... go for the soldier taunt kill.
He blew up, took a couple players with him and it immediately devolved back into chaos. It went from absolute peace, to just your standard game of TF2 in the blink of an eye. I always think about that moment.