Several of the California National Guard troops are depicted as being armed with M16A1 rifles (distinguished by their smooth, triangular forward hand-guards and three-pronged flash suppressor). The National Guard phased out the M16A1 in the 1980s, replacing it with the upgraded M16A2 (ribbed, rounded forward hand-guards, and an enclosed, "birdcage" flash suppressor).
(at around 1h 28 mins) The breast pockets on Betty Ross's denim jacket switch from buttoned to unbuttoned between shots when she is confronted by David Banner in her house at night, and again, later, when she approaches the Hulk in downtown San Francisco.
(at around 17 mins) When Talbot first talks to Betty as she's entering the building, the screen cuts in half as per usual throughout the movie. In one shot, Betty's hand is on the upper part of her pocketbook strap. In the other shot, it is not. The two shots are not in sync.
(at around 1h 45 mins) After the exchange with the tanks and helicopters, Bruce heads for home by leaping across the countryside. He lands with a foot on the road and one on the grass near a road sign marked San Francisco 61 [miles] Berkeley 65. There is significant damage to the tarmacadam road but virtually none to the earth at the side of the road.
The two men operating the top-mounted machine guns on the (fake) Abrams tanks would have been the tank commander and the loader. The loader, however, never drops back into the tank to load the main gun, yet the main guns on the tanks fire at the Hulk several times when they encounter each other. In addition to that, as tankers are running away from one tank after losing the turret, only two of them are seen, instead of the 4 men in the crew of an Abrams tank.
After Harper short circuits the motherboard on the Gamma System, Bruce pulls him out from within while Harper simultaneously puts on a form of gas mask. The next clip shows the plastic bag filled with nanomeds emptying, implying that Harper was pumped full of them. However, because the mask wasn't hooked up to the dispersal machine, there was no way Harper could have inhaled them, and, as far as we know, no reason for Bruce to need to jump in front to block him from the rays.
(Around 1:49:47) When Hulk thuds into the water after being thrown off the jet from space, the splash is seen to rise only a few feet in the air. However, from such a height, the water would have splashed up for at least several miles.
The last Spanish words spoken by Bruce are incorrectly translated. The subtitles say: "You're making me angry. You wouldn't like me when I'm angry" but he actually said: "Me está enojando. No le gustaría verme enojado" ("You're making me angry. You wouldn't like to see me angry").
The goof item below may give away important plot points.
(at around 1h 6 mins) After the Hulk kills the dogs and goes to the river to cool down, from the rear Bruce Banner appears naked, but as he approaches the car where Betty is, you can briefly see he is wearing skin-colored underwear which he tries to cover with his arm.