Section 86a of the German criminal code, the Strafgesetzbuch, makes it illegal to display the symbols of "unconstitutional organizations". That makes it rather tricky for a game such as the newly-released Wolfenstein: The New Order, which is all about murdering Nazis and blowing up their stuff, especially because Nazis liked putting their symbols all over themselves and their stuff. Verboten in particular are the swastika, the celtic cross, and the SS sig runes.
To comply with German law, Bethesda published a special version of the game in which all of the illegal symbols have been scrubbed out or replaced. Eurogamer put together a fascinating side-by-side comparison of the German and non-German versions of The New Order to show all the work that goes into erasing the bad signs of history.