People who don't pick up their dog's poop at the park.
Oh, you think I like picking up my dog's stinky poop? (Although she thinks it smells like roses) No, I do it because it's the courteous thing to do. And I don't want to step in a pile of poo. I would feel terrible if that happened to someone because of me. So please pick up your dogs' poop. It will make this world a better place (and a little less sh***y).
There's even a song about stepping in dog poop.
And a BIG THANK YOU if you pick up after your dog!