People Who Park Carts In The Middle of Aisles
When I am emperor, I will round up all of the people who block the aisles of stores with their shopping carts, seemingly oblivious to anyone else who wants to walk or, worse, wheel his own cart down the aisle. I will take away their drivers licenses, as I clearly cannot trust them with motorized vehicles.
I will confine them to their houses (and possibly bedrooms) until they can complete a timed obstacle course where they must navigate through seemingly wide corridors made almost impossibly impassible by stacks of irrational objects placed at random in the most annoying configurations possible. I will also have my minions duct-tape their arms to their sides so they cannot push lighter obstacles out of the way.
Ravenous hordes of angry teenagers may chase the guilty through the course, throwing fruit and vegetables at them. I haven't decided whether the fruit should be fresh or rotten.