Leaving things they decided they don't want just wherever in a store. It's annoying as a customer, because now I have to dig through their mess to get the product I actually wanted, and even moreso as an employee.
At least put it back in the right department. The underpaid employees who have been there since before the store opened for the day really don't want to have to play the game of "How long has this ground beef been sitting in a produce basket, and how much product did we just lose?"
I remember a story of a guy talking about how the store reeked and smelled terrible. After doing tons of searching at the epicenter of the smell, turns out some guy hid a 5 pound beef brisket on the bottom shelf, hidden behind a bunch of breakfast cereal.
You can and will find terrifying things working in grocery.
I once found a pack of beef jerky that had become 90% mold. It was tucked all the way towards the back of the shelves, partially shoved into the crack between two of them. We had no clue how long it had been sitting back there, because jerky rarely needed a full teardown.
Found a package of ground beef randomly hidden in the very back of the milk cooler. Thankfully kept fairly cool, and still in date, but a customer had stuck it there because he wanted to come back later. He came back the next day and tried to file a complaint because it wasn't there.
Fish left in the bathroom. Like, straight up a pack of salmon fillets, just left there on the top of the toilet tank. Our best guess was that someone wanted to steal it, but either couldn't fit it or got spooked and just abandoned it. It was in a far corner, barely used bathroom, too.
Half eaten fruit or candy thats been shoved to the back of a low shelf. You know a kid did it, there's massive mess back there, and depending on what aisle they hid it in, it might have been there for a couple days to a week. Once found a bell pepper some kid had chomped into.
This is more just "general trash", but still not uncommon if your store has a hotbar: Stolen food containers. People grab their dinner, eat it throughout the store, and then just put the trash wherever. If you're lucky, they leave it somewhere obvious. If you're unlucky, you find an open container of half-eaten rotisserie chicken shoved into a vent after they turned the heat on for the winter. Going past the deli in my store has triggered minor PTSD at times. That smell... Just... Hot rot. That's the only way to describe it. Rotting garbage, oven warmed.
The deli in my store was right next to the bakery. So in the morning there would be the amazing and overwhelming bliss of freshly baking cinnamon rolls combined with the disgusting pile of little bits of meat from the slicers.
We had flies pretty bad. I remember going around to check temperatures in the open face coolers. The flies would land in there and just sort of freeze. It was icky.
I think there's some misconceptions about this that need to be cleared up. If you don't want it and you've already moved away from the section, the best thing to do is take it to the register and say you don't want it. Then what typically happens is it gets put in a take-back cart and the employees take care of it
One of my stranger experiences as a cashier was watching someone waiting to be checked out change their mind and start trying to abandon some ground beef among the candy bars at the checkout. Apparently handing it over to me didn't occur to them. At least when I pointedly offered, "If you don't want that I'll take it." they handed it over.
No, it's not. People often forget where they got it from, and it might have been in the wrong place to begin with or already expired. Take it to the front.