Setup: Playing Shackled City, the end of Flood Season. Group stands on a cliff face overlooking a subterranean lake, alight with glowing algae. The only way across appears to be a metal cage attached to a winch-pulley apparatus, the ropes for which span the lake (kind of like a ski-lift, I suppose). The near end of the rope is attached to a winch/gear mechanism attached to a guard house on the top of the cliff. The far end is attached to another guard house on the far shore of the lake, which is about 100' below the level at which the group stands on the cliff top. Thus, the ropes have a downward slope to them from the group's POV.
Anyway, the spellthief decides to "zip line" across, gets halfway over, loses his grip, and falls fifty feet into the lake. A skuvyn demon in the lake soon sets upon him and matters look dire. The warforged and two others disable the gear safety on the winch and dash into the cage, now free to speed down the rope lines. Below them, the spelltheif is in dire straits. The warforged fighter takes position in one end of the cage, takes firm hold of the bars, and readies his glaive. As the cage passes over the combat between the spellthief and skulvyn, the warforged cuts the ropes.
He (and two others, ignorant of his plan until he did it) ride the plummetting cage toward the lake, the skulvyn, and the spellthief. He thrusts his blade between the bars as they fall, hoping to crush and impale the skulvyn all at once.
Very cinematic move, but he missed the skulvyn altogether, and instead clipped the spellthief with the cage. While the other party members scrambled out of the cage, the warforged rode it to the lake's bottom. As he descended, the skulvyn set upon him and they had a balrog-gandalf running battle. They hit bottom and continued the combat, with the warforged getting the better of the demon and gradually dragging him into shallower water, where he and the rest of the group finished it off.