My brother once straightened a buckled front rim on his BMW R60/5 (alloy rim with wire spokes) on the side of the road by bashing it with an axe that he borrowed from a local farmer. He did it properly though, using a lump of firewood between the axe and rim to soften the blow. The dent actually came out nicely and didn't need any further attention.
The rim got dented by running over a brick on the highway at about 100kph. I presume the brick fell off a truck or something. He was following close behind a car, about to overtake. The car blocked his view of the road surface ahead. As the car straddled the brick, it suddenly appeared on the road right in front of bro's Beemer and he didn't have time to dodge around it. The impact splayed both sides of the rim out. The tyre (inner tube) didn't deflate though and he didn't crash. His rear wheel also ran over the brick but wasn't damaged for some reason. Maybe he'd bounced off the seat and unloaded the rear end by the time the wheel got to the brick.