We have a whole FB page dedicated to bad parkers here.
Apart from this my biggest beef is people who park in disabled spots without a permit (no excuses!!!!!!!) and the parallel parking out the front of DS's school. I've often had to do laps to find a park because people will leave not quite a car space between them and the car behind them. There is one person who shouldn't have their licence because they seem to have no idea about how to reverse a car. I watched her one day. She was pretty straight but when she tried to reverse back towards my car she somehow managed to hit her back tyres against the kerb and have her front end sticking out about 2 metres
But really, parking and reversing are things that really do matter when it comes to driving.