Stupidity: When an explosion hits the courtroom, Arthur is the closest person to it, with nothing to protect him, but he is the first and only one to recover, and every bailiff (not to mention the police outside the courthouse) outside of explosion range is mysteriously knocked out and/or absent.
Stupidity: When Eitan and Ran escape the Egyptian troops, they take shelter in a creek and fire back at them. Ran is firing from his handgun, but the troops are at least a couple of hundred meters away, while a common handgun can only reach a range of about 30 meters. There is no way the handgun's bullets will even reach the chasing troops. (00:57:24)
Stupidity: During the battle on the harvester, Chani is firing an anti-aircraft projectile at a Sardaukar approaching her. Although the projectile is strong enough to destroy an ornithopter, instead of blasting the Sardaukar away, it pushes it into the air until it hits the harvester track. (00:36:39)