Other mistake: It's raining when Nameless and Sky are fighting (rain is dripping off their swords and is on Nameless' face when going towards Sky in slo-mo), but their entire bodies never get wet.
Other mistake: In the scene where Mel Gibson fires off a few rounds into the nearby woods and bushes to see if there are any NVAs, there is a M60 crew, the weird thing about them is that you can only see the muzzle flame from the M60 the first couple of rounds - after that there is no muzzle flame, but the M60 continues to fire at the same rate.