(at around 48 mins) When Wax bursts into the terrorists' apartment through the window and shoots the first terrorist, we hear only one gunshot from Wax's gun but two bullet holes appear on the first terrorist's torso.
When Reese is running up the spiral staircase following Wax, bodies are falling down the stairwell. When the 4th body falls down it makes Reese jump and some of the powder pops out of the vase he is carrying in his left arm onto his shoulder, in the next shot there is no powder on the shoulder.
When Reese is at the sink to wash the blood off of his face after destroying the pushers' lair, he raises up and looks in the mirror after his first rinse off. There is still a large patch of blood on his left-top forehead. When it cuts to his CU, the blood isn't there and he hasn't washed it off.
When Charlie uses his watch to send coordinates to the satellite, the satellite zooms in on a location northwest of Paris. The coordinates Charlie sends (48.79, 2.337) are actually south of the city, near Orly Airport.
When Reese is watching for drug dealers through binoculars while Wax is in the other room with a hooker, you see Reese looking through the binoculars correctly. Shortly after, Wax takes over while Reese answers the door. Wax can be seen holding the binoculars back-to-front (inverted).