People who come out of ikea with their trolleys full of stuff and then hog a parking bay while they wait for 10 minutes for their driver to come and park, thereby causing a huge tailback of cars who can't park to be loaded up because all of the bays are being hogged. Whyyyy! Just wait out of the way for your car to arrive!
And then there's the people who finish unloading and then just leave their trolleys blocking the way for the next person 
It's probably the same arseholes who repack their bags on the conveyor belt at airport security instead of lifting the whole tray out of the way on to the tables nearby.