Although this is the english Saints Row Wiki, this wiki is not only about the english version of the game: all information about different versions and languages is welcome.
Some of the most well known differences are the changes in the German, Japanese and Australia versions of the game.
Here's a site that details many of the differences in the German low-violence version of Saints Row 2: http://www.schnittberichte.com/schnittbericht.php?ID=5975611 (Some of that information has been added here already.)
Many translations use alternate names for missions which make more sense in those languages, and that kind of information about subtle differences is also welcome here.
So if you play Saints Row in a different language, feel free to add trivia on how it's translated into your language.