Mine was a few years back when I had just finished building a Nicolai up. First ride went to my local spot drove into the car park went for the ride. Smiles all around, put the bike back onto the bike rack on the roof went to drive out of the car park and the council had decided to close the bar to stop trucks getting into the car park... Bike managed to stay on the rack but the bar dented the steerer and top tube where the bar came to rest.... it also damaged the stanchions of the forks.
Journey home was full of mutterings of "f**king idiot.

