(at around 37 mins) When Mike and Rudy get into a fistfight, twice Mike pulls his gun and you can hear the sound of the hammer being cocked. Both times, you can see the gun and the hammer is clearly down.
(at around 28 mins) When the group arrives at the village, the corpse of the Portuguese is decomposed far more than it would normally be after one day, even in the rain forest. Also, other people who died before him weren't decomposed at all.
Rudy wears a neckerchief bearing the OshKosh logo, but the lettering seems to switch between being a 'mirror image' of itself (so it reads hsoKhsO) and appearing as it should, often several times within one scene.