Revealing mistakes

When Bone knocks Hammerman out and he falls to the floor, you can clearly see that the concrete is fake as it creases when Hammerman's head hits the floor.

Crew or equipment visible

In the first scene where Kimbo and his companions are walking, the camera man's shadow can clearly be seen on the railing below.

Continuity

When James is discussing talking to Franklin McVeigh the hilt of a samurai sword is visible. In the next shot, the sword has disappeared and never reappears.