When Sloan is showing the punk some moves, he suddenly goes from having no sunglasses on to having them on.
The dead girl in the holding cell can be seen breathing.
In the final battle between David and Tong Po, you can see the latex on the back of Tong Po's head, start to come off.
During the fight on the bar, against the bikers, one particular biker is beaten by David a couple of times, without breaking a window. After another character hits him by mistake, and they break the window and fall to the other room, the fake wig with the scarf is seen on the side of the knocked out biker.
Numerous shadows of cameras and lighting equipment in the fighting ring on the floor and the fighters.