Not only did we have a marvellous picnic, but I finally learnt how to play mafia games. In it, people in the group are either ordinary citizens or mafia (red or black cards) and then there are other roles to complicate things. The final aim is that either all the good citizens die, or that they manage to kill the mafia (although the game is inherently loaded against this outcome). So you play out a series of days and nights (during which citizens have eyes shut, mafia can see and choose who to murder.) During each 'day' everyone discusses who is the mafia, and makes accusations.
Of course this circles the difficulties at the centre of a corrupt society; if someone talks to much, that can make them seem likely to be mafia, as they are trying to point the blame elsewhere - but of course if you say nothing then you are also likely to be mafia, because you are trying to stay invisible. So the game is actually about hilarious, philosophical, joyfully argumentative talking.
Just a reminder (from my previous post on this subject) that you can read the original Mafia Games rules here and a more detailed explanation and brief history on Wikipedia.