Even a simple charging cable can contain e.g. a HID chip while still working as a charging cable. I saw an unattended cable on a table at work once, I'm sure someone who needs one would've used it without second thought. But our employer is also sending fake phishing emails to make people aware, I wouldn't be surprised if they also plant devices like that.

...and if they don't I should propose it, sounds like a fun project. Leave a random cable or USB stick that just shows a warning that it could have been malicious. Or something that just opens up https://nyan.cat and sets the volume to max :D.