What happens if you are caught (accidentally) not declaring something at customs?
So, you get into the "nothing to declare" line, but you get selected for a random bag check anyway... and the customs officer finds something you were supposed to declare.
It's something small, like a plant product, or something that you are supposed to pay a duty on. But you either forgot you had it or didn't realize you were supposed to declare it.
We're definitely not talking about drugs or anything else that would land you in really hot water.
What happens next?
FWIW there are reality TV shows on which this happens *all the time*. No doubt the show doesn't represent the full variety of what can happen to you, but they've shown food products in UK or Aus they've been destroyed, sometimes a fine. One showed cannabis taken and destroyed with no action against the person carrying it, by Canadian customs on the US border. I've also seen people arrested/deported when they're believed to be intentionally smuggling. But I've only ever seen a few episodes, only English-speaking countries, and this is the incidents that customs chooses to film and release.
... so, if you're worried about being stopped by customs then it might be worth finding a show for the country you're travelling to, just so that you know what you're worrying about and what processes you'd face. And then, like, pay attention to the law and check your pockets and luggage.
In Switzerland it will depend if it's an illegal article or if you fail to pay duty.
In the first case (if it's mildly illegal, usually counterfeit watches, I'm not talking guns or anything) they'll just seize it and destroy it, no fine involved. There is a slight chance that the copyright owner might sue you, but I think the chances are you'll just lose the product but be fine. I guess the same will happen if you take some seeds or some meat from outside the EU or something else that's prohibited.
If you fail to declare something that you have to pay duty on however, you're likely to have to pay a fine on top of the duty fee. That happens quite often to people buying meat on the other side of the border.