Modern Vespa

People who think it is ok to hold up traffic because they decided they want to make a left turn at the last minute.

To make matters worse, they make that decision while in the far right lane. So instead of just finding somewhere to turn around, they basically sit with their turn signal on holding up traffic while trying to get across two or three lanes to get to the left turn lane all the while backing up traffic. Cabbies love to do this.

Related to that are the people who drive real slow because they are looking for a turn or an address instead of just proceeding normally and risk having to make a u-turn. The make their problem everyone's problem.