I've occasionally ran moral quandary type plots which can be quite revealing.

There was one where I had an evil young cultist going around sacrificing children. After a lot of effort in tracking him down, they caught him and took him into custody. The locals formed a lynch mob which the party held off. They then took him off to the city for trial — well actually they allowed the Paladin of Horus to take him to his temple. The trial was brief, and the sentence capital. Apart from one player (the paladin as it happens) the rest of the party split along their real world views on this matter.