Soldato
My other favourite is people driving around with their wing mirrors in.
It just beggars belief, the fact that they've not even noticed that they're folded in just tells me that they're so oblivious to their surroundings that the mirrors aren't even required. I reckon you could restrict half of our drivers' field of vision to 15deg and they wouldn't even notice.
What worries me is that our company are wanting to switch to cameras rather than physical mirrors. Unlike mirrors they can't be adjusted. I like being able to adjust them as I tend to move them out and slightly down from where other drivers have them to give me a wider and lower picture from my driving position which reduces some of the blind spots.