Stepping into someone's big steamy wad of gum while loading your car in the Target parking lot.
Except maybe stepping into someone's dog's big steamy wad of poop. That doesn't happen as much these days since all the pooper scooper laws went into effect, and dog owners don't let their dogs run loose like they used to. Back in my elementary school days the worst thing that could happen when you got on the school bus was for everyone to start yelling 'eeeewwww, who stepped in dog doo?' We didn't call it poop back then, I don't think that word had been invented yet. Dog doo was dog doo, not poop, shit, or caca. And people did not pee and poop, they went number one or two, or tinkled and bm'd.
So, anyway, here I was, stuck to the pavement by a big wad of nasty gum, trying to scrape that shit off my shoe so I wouldn't trail gooey gum into the car.