When Steve leaves the governor's office to see Danny in the hospital, he is driving a 1968 Mercury four door sedan. When he is speeding down Nimitz Highway, he is driving a 1967 Mercury two door sedan. When he arrives at the hospital, he is in the 1968 Mercury again.
The limo that picks up Lin Mai-Lu is a 1966 Cadillac. When they arrive at Hummel's estate, it is a 1972 Cadillac.
As McGarrett (and the Governor) leave the airport in a limousine, McGarrett is wearing a dark suit, yet, when he arrives at the destination, he exists the limo wearing a light-colored suit. Furthermore, the black limousine changes three times: from a '66 Cadillac, to a '71 Lincoln, then to a '72 Cadillac.
When the boat with the dummies on board explodes, a much smaller craft is seen burning.
When Danny Williams (James MacArthur) is first able to remember the events at the bunker when he was fired upon while horseback riding, there are several overlapping or multiple exposure shots in slow motion showing him simultaneously riding his horse and walking toward the bunker (to simulate his fragmentary memories). Then just before the first shot is fired at him, there is a clear image of what is supposed to be Danny on his horse, but it is obviously a stuntman or double on the horse, not Danny.
As Danno attempts to flee on horseback from outside the bunker, gun shots are fired directly at him, but seemingly do not strike either him or the horse.