Factual error: In the scene in Stuttgart, we see a "reserved parking" sign written as "Reservierten Parken". First of all, this is grammatically wrong - if used at all, it should be "Reserviertes Parken". But you wouldn't find a sign in Germany saying that. They say "Reservierter Parkplatz".
Continuity mistake: Throughout the film, Tony Stark's chest ring can be seen glowing through his shirt except for two occasions when it's suddenly off - after Loki escapes from the helicarrier, and when Loki and Tony Stark are talking in Stark tower, even when he's wearing the same shirt.