Revealing mistake: Director's Cut Only: After Godfrey's party has been attacked in the woods, a surviving noble is executed by the sergeant. We see his axe strike from behind, then the shot cuts to show the face of the noble as the sergeant pulls the axe out and off-camera. As the noble slumps forwards, the axe reappears in frame from below and it can be seen that the axe has no forward point, allowing it to be placed against the head of the actor playing the noble as if embedded. (00:29:25)
Visible crew/equipment: When the Muslim armies approach Brendan Gleason's castle there is a side shot of the Muslims army coming to a halt. You can see the marker stake with yellow tape at the top (used during production as a mark). (01:10:10)
Other mistake: At Kerak, as the 2 armies are facing off, the wind is blowing the banners of Saladin's army hard to the left, but as the view switches to Baldwin's army, facing the opposite direction, their banners are also blowing left. (01:33:00 - 01:33:50)
Continuity mistake: As Orlando Bloom is talking to his bald comrade walking through lined up guards, after they realise the enemy has arrived, neither is wearing armour. As they stroll through the arch, you see that both are now wearing armour. (02:18:05)
Continuity mistake: Just before the end of the movie in a scene where Balian and Sibylla ride on horses, they briefly stop next to a concrete cross and we can see village/houses in the far background (middle of the screen). In the next scene we can see all these houses being removed/replaced with woods. (03:00:10)
Factual error: The crescent as emblem on Saracen pennants is anachronistic as it appeared on Islamic military flags no sooner than the 15th century A.D.
Factual error: The Patriarch of Jerusalem was (and is) not addressed as 'Your Eminence', which is reserved for Cardinals, but as 'Your Beatitude'.
Factual error: The title (as opposed to the name) is spelt 'Marshal', not 'Marshall' as it appears in the caption when Balian first meets Tiberius.
Factual error: Jerusalem isn't situated in a dry barren desert as it is in the movie. The view East from the walls of Jerusalem is toward the Garden of Gethsemane and the Mount of Olives (from where Saladin attacked on 20 September 1187).
Revealing mistake: When the Muslim emissary arrives to Jerusalem and Guy de Lusignan stabs him under the chin, look at the blood. It bursts from something attached to his shoulder. In addition, the emissary is seen as stabbed with a small dagger but then Guy De Lusignan is shown holding a full length blood tipped sword a second later.
Continuity mistake: When Balian is talking with Tiberius after denying the King's proposal, watch Balian's clothing. His chain mail is visible on both sides of his shoulders in one shot; we cut to Tiberius for one line (I believe it was, "Jerusalem has no need for a perfect knight") and when we cut back to Balian, his cloak is now covering the chain mail completely.
Factual error: It is mentioned that Saladin has crossed the Jordan River and is on his way to Jerusalem. Balian then rides to Kerak to defend the city. But Kerak is situated East of the Jordan River and South of where it runs into the Dead Sea, so Saladin would reach Kerak long before he crossed the Jordan River.
Revealing mistake: The shields carried by the crusader extras in the marching and pre-battle scenes, etc. are all made from the same casting. Some differ, but the majority have identical battle damage, gouges and slashes.
Audio problem: When the Christian army is defeated after chasing Saladin across the desert, many vultures are flying over the battlefield. However, the sound is that of a flock of whooping cranes.
Factual error: The warrior-monks of the Hospitaler and Templar orders were not priests, although they did have attached chaplains. The Hospitaler should therefore not have been able to give Godfrey the Last Rites.
Continuity mistake: Right before the scene where the camp is attacked, the snow on Balian's head changes.
Continuity mistake: When Balian is considering killing the Muslim servant after killing his "master", his sword is placed straight into the ground. In the next shot showing the Muslim's face, the hole is considerably bigger.
Factual error: In 1184 Golgotha wasn't a barren hill outside the city walls (where Balian goes to reflect in solitude). It was in the middle of the city and there was (and still is) a church on the site.
Other mistake: When Balian talks to God on the hill where Jesus died, after he says his line, the next shot is him sitting down overlooking the empty valley below. A white light travels from right to left going 45-50 mph. Nothing back then could go that fast, and even if anything could, a torch is yellow and red, and even if it could be white, no rider can ride that fast with a white-light torch and keep it from going out - leaving us to assume it's a car.
Continuity mistake: In the scenes before the battle at Kerak, the skies shift from totally clear to quite cloudy and back again in the various shots.
Answer: I thought it was cotton with oil of clove for a bad tooth.