Continuity mistake: When Hulk throws the chunk of sheet metal at the helicopter, it glances off the rotor housing (taking a ragged piece with it.) When the chopper crashes, however, the propeller comes off with a perfectly clean edge, as if the projectile had sheared completely through the base.
Continuity mistake: After the first time we see Bruce transform into the Hulk, he has hitched a ride with the elderly man. You will remember he has 3 1/4 length pants on with a few rips. It cuts to a quick clip of him walking up the road but this time he has full length pants on. They switch back to shorter length pants straight after.
Continuity mistake: When Abomination pins Hulk to the wall, and Hulk starts to push back, at first, when the camera view is level with their heads, Abomination's left hand is grabbing Hulk's right forearm. But when the camera view lowers to their abdominals, Hulk's right hand is grabbing Abomination's left forearm.