This one is no contest. Though I'll also give you a runnerup.
Things of this nature have happened a couple of times, actually. With this specific pair of players. One of them, if he ends up playing a certain kind of class, and has a spear, he'll be jumping from things onto enemies. No question. And then there's the occasional partner in crime...yeah. So one of these "Flying Circus" times, there were kind of tower-y buildings, and there was a harpy well, harping us. Harrying us. Before any leaping occurred, the harpy got crit in a sensitive area with a football sized rock. Then, well, a member of the flying circus leapt from the top of a tower to attack her and, the way the rolls worked out, essentially ground her face down the side of the tower like a skateboarder grinding a rail.
The same pair, but with different characters, did this at least one other time in my sight/memory, where they leaped across a chasm to a ledge/cave on the other side, to attack the monsters that were there (troglodytes? kobolds? I don't remember). I think there was yet another time, when an otyugh was leapt upon from a decimating height.
The other craziest thing was more like a chain of crazy thing, across the 13 or 14 levels of play we had in the Temple of Elemental Evil. Wherein the gnome rogue (remember, the one I killed another player to defend?) lost his hands/arms a total of...8 times? 7? He also died at least two times, it might have been three. He certainly earned the, er, deed name of "Many Arms". Most of the time it was his left arm that it happened to, but when he got sucked into some kind of demonic machine towards the end of the temple, it took his right arm and replaced it with a blue tentacle. We, er, fixed it.