Before Eric climbs up from the sewers, he sticks his gun behind his belt. After he gets shot by the maniac, he falls back into the sewage. In the next shot he picks up his gun (which is completely dry) from a stone beside the water.
When the old man that lives on the barge loads the shotgun, you can see that the primers on the shells have indentation marks in their centers, signifying they have already been fired.
During the utterly ridiculous speedboat chase both boats pretend to be in a James Bond movie and are jumped onto the embankment, slide along the path and back into the canal.
Just before Eric's boat drops back into the water the wheels attached to the bottom of the boat are clearly visible.
Early in the film Eric drops his daughter off at school. He then pulls away and drives straight through a red light.
The scene at 13:00 where Eric gets stuck behind the truck while in his car and witnesses/intervenes an ongoing robbery at a bakery is not filmed in Amsterdam but on the Vismarkt in Utrecht (where they speak with a totally different accent than 'Amsterdams')