The rules of being a house guest are relatively simple: clean up after yourself, say please and thank you, and don't touch anyone's things without explicit permission. Of course, there are a myriad of more nuanced social mores to take into consideration when you're a guest, most of which require emotional intelligence. But when it comes to the basics, it's not that hard to be considerate in someone else's home.
Sadly, however, there are plenty of people roaming the world acting deeply inconsiderate in other people's homes. Some people are so rude they manage to tear apart relationships with their antics, and while it's sad for the people they alienate, it can make for a juicy story.
A guy we didn't know very well, a friend of a friend, came over to our house for dinner one night. He got quite drunk, despite not knowing him very well we offered that he stay the night at our place instead of driving home drunk. He refused, drove drunk and crashed his car. Then he tried to sue us for letting him drive home drunk. The guy was an a*shole.