Stupid people who think the best place to let their dog(s) crap is right in front of their propane tanks. I've got to the point now I won't fill their tank if I have to drag the hose through dog shit. How hard is it to clean up after your dog? Freeze. I don't care.

A close second is the people who plow their steep, winding mountain driveways just wide enough for a Jeep or Subaru and then complain that I didn't deliver to them.

Some people are just too stupid to own a dangerous substance like flammable gas. They should have to go through background checks and waiting periods.