Probably recently, when I was playing Halo 3 4 player co-op and we were at the point on The Ark where we had all grabbed tanks and were rolling about leaving a path of death, destruction, despair, and other words that begin with "de" in our wake. It was right after the "Tank beats EVERYTHING!" line. I was in a tank behind my two friends, who were also in tanks. The friend directly in front of me started rolling over the friend in front of her, while at the same time I slipped the treads of MY tank under hers, and then suddenly she disappeared. According to her, she had lifted into the air and began flying and spinning out of control. The funny part about this is that all the while it was going on, I had no idea it was. I just noticed my friend had gone missing and had quite the "WTF?" feeling.
I later viewed the saved film, which, while clarifying what happened, still left me with a "WTF?" feeling.