The Guardian has an entertaining article on traveling, different cultures and how you can break the law through misunderstanding local traditions.
It's illegal to WHAT officer? from Guardian Unlimited: Travelog
The same as when we make these lists of weird laws in the US, there are some that just don't make sense (flushing the toilet after 10pm in Switzerland) or some penalties that are pretty severe (death for bringing pork into Yemen) or just weird (illegal to kiss on the railways in France - I'd weigh in that a train in France would be pretty romantic).
But I just love how the Brits use snog: " And don't snog that hottie till you finally reach the Gare du Nord."
I'm a big fan of snog.