Anti-Nazi Symbols
The movie takes particular glee in subtly deflating the various symbols of Nazism. Sure, we get the gist of it whenever our hero pounds some goose-stepping moron senseless, but Raiders just loves ridiculing them whenever it can. We get a shot of a monkey giving the Nazi salute, after all, and you don't have to be a semantics expert to figure out what that means.
Similar images crop up every few minutes: Sallah using a German flag to create a makeshift rope in the map room; Indy pulling the Mercedes hood ornament off of the truck as he hangs on for dear life; the Ark itself burning the Nazi symbols off of the crate containing it. It ain't subtle, but it does the job, and when God's holy fire burns the Nazis to a crisp at the end, you can't accuse the movie of waffling on its opinions about them. Way to go, movie!