Continuity mistake: During the hallway gauntlet, Oliver takes a guy out and ends up on his left knee. He then starts to turn right and draws an arrow, which doesn't make any sense because he holds his bow with his left hand and can't get a good shot from that position. What's more, in the following shot, he is turning to his left.
Audio problem: When Oliver is fighting the guys in the hallway, he shoots the second to last guy. But when he starts to draw an instant beforehand, you can see that his right hand, with which he holds the arrow, is nowhere near the quiver when the sound of the drawn arrow begins.
Factual error: When The Hood busts into the underground casino, the throws a guy through a glass table, and it breaks into large shards. He then proceeds to grab a handful of safety glass, so it's not the same glass anymore, and he throws it into the face of a guard, and it hurts him badly. Safety glass is designed precisely to prevent that. It is impossible for the pieces to get lodged in the guys face, no matter how hard The Hood throws them.