In their very first scene when Aragorn, Legolas, and Gimli are seen running on top of a mountain, you can see Gimli's boot/shoe fall off.
When Aragorn is lying on the river's shore, he forces himself onto an unsaddled horse. But, when he sees the Orc Army and starts to gallop towards Helms Deep, he is riding with a saddle.
Pippin's hands are tied, but when he falls under the horse, his hands are untied and apart. When Aragorn is working out what happened we see, in the flashbacks, that Pippin did not cut his bonds until after the horse incident.
Legolas' eyes are brown for the majority of the battle of Helm's Deep, instead of their customary blue. However, it is reported that this particular color change came about when Orlando Bloom's blue contact lenses were forgotten during some of the shooting for this sequence.
When Gandalf the White first enters Theoden's hall, the position of his staff changes from being held perpendicular to the ground to being held parallel between shots. Director Peter Jackson noticed this error for the first time while recording the Director's Commentary for the Extended Edition of the DVD.
During the battle with the Warg riders, a Warg and Orc fall across Gimli. Visibly struggling to lift them off, there is no change in effort or position when a second Warg puts its weight on Gimli. This should be an addition of several hundred pounds.
In the extended DVD edition, Dominic Monaghan points out in the cast commentary that in one of the aerial shots of the Uruk-Hai taking the Hobbits to Isengard, Merry and Pippin are nowhere to be seen. This is false. Both Hobbits are wearing green capes which can be easily made out without freeze-framing the scene. The Hobbits are being carried by two Uruks in the third line from the front of the group. (Extended Edition DVD Time Code: Disc 1, 26m20s)
Aragorn tells Éowyn to set Brego free as "he has seen enough of war."
Yet, after Brego later rescues him, Aragorn uses him as his own horse, even in battles such as the final mounted charge at Helm's Deep and throughout The Lord of the Rings: The Return of the King (2003). (Brego's distinctive white star on his face can be seen each time.)
This is not a Goof but simply a change in circumstances that forced Aragorn to make a difficult decision.
This is not a Goof but simply a change in circumstances that forced Aragorn to make a difficult decision.
When Aragorn, Legolas, Gimli and Theoden ride out in the Helm's Deep battle, the back row of Rohirrim soldiers are swinging their swords at nothing.
Several shots after Legolas, Gimli and Aragorn encounter Eomer and his men have been reversed (leaf-brooches are upside down, and Legolas' chest straps and quiver are on the wrong side).
At Helm's deep, several elves draw and shoot their bows (complete with sound effects) but no arrows are seen.
In Helms Deep, when people are moving deeper into the caves (as orcs are storming the keep), we see a woman put her hand on one of the stalactites as she passes it. When she releases it it sways gently.
At times the character Gimli is as tall as Aragorn's shoulders. At other times, he is much shorter. The same error can be seen in The Lord of the Rings: The Fellowship of the Ring (2001) when Gandalf and Bilbo embrace.
In the battle of Helms Deep, archers are ordered to "fire". Such an order is for a gunpowder weapon. In the age of the bow and arrow, the order to "fire" would be meaningless. The order would be "release" or "shoot".
Saruman's Uruk-hai - having captured Merry and Pippin - are supposed to be running back to Isengard, but as the camera pans downwards to show them for the first time, it's clear that they are just walking and only start to run as the camera points directly at them.
When Shadowfax first appears, there are tracks across the paddock behind and to the right of him. Some say these are tire tracks, others argue that they could just as easily be the wheel ruts of a farm cart. In response, the first group say that the ruts are too far apart to be from a farm cart, and the space in between is too narrow, meaning that they are definitely those of a car or truck.
During the second close-up of Legolas's eyes in Fangorn Forest, you can see that he is wearing contact lenses.
When Gollum is being interrogated by Faramir and lies facing away from the camera, his fingers keep getting mixed up in the flesh of his back.
When the Rohirrim surround Aragorn, Legolas and Gimli at the beginning, you can see Éomer's lips moving in one of the wider shots and he obviously talks to the three but there is no sound coming out of his mouth.
When Saruman is talking to the Uruk-Hai, they are obviously screaming and yelling, but there is no noise coming from them.
During the trek to Helm's Deep, right after Gimli's horse runs off and he falls from it, Théoden turns to Aragorn and begins to speak yet no sound comes from him.
In the Extended Edition, when Merry and Pippin find Saruman's food storage, You can hear Merry whispering "Saruman's store," but his lips do not move when he starts to say it.
When the Uruk-Hai are approaching Helm's Deep, they sound like all of them are marching in complete lock-step, even when they're marching on uneven terrain and around obstacles.
In the battle of Helm's Deep, when the Uruk-hai are about to ram the gate, a camera is seen in the left.
A small gas pipe, leading to one of the large torches outside the Golden Hall, is briefly visible in some scenes in Edoras.
During the Battle of Helm's Deep, right after Legolas slides down the steps on a shield, there is an upshot of him killing an Uruk-Hai. In this shot, a piece of modern pipe can be seen attached to the wall behind them, likely a raintree.
When Éomer is walking through the fallen looking for Théodred, in a brief shot towards the ground what looks like a yellow safety vest with a reflector stripe is visible among the corpses. There have been suggestions that this could be part of a banner, but it bears no resemblance to any banner relevant to Rohan.
While Aragorn, Legolas, and Gimli are tracking the Uruk-hai, Aragorn asks "Legolas, what do your elf eyes see?" And Legolas responds, "The Uruks turn northeast, they're taking the hobbits to Isengard!" If the Uruks turned northeast, they would be traveling away from Isengard, since Isengard is northwest of their location.
The fight between the Rohirrim and the Uruk-hai took place at the southern edge of Fangorn Forest. Later, when Eomer leaves Aragorn, Legolas, and Gimli, having just told them about the battle, he calls out to his company to ride North - the direction they had just come from.
During the battle of Helm's Deep, after the wall has been breached and Haldir dies, Aragorn gets on an Uruk-Hai ladder and drops himself into the advancing Uruk-Hai. In the wide shot it can be clearly seen that the ladder has been raised against the Deeping Wall from inside the castle. When, how and why did the Uruks raise a ladder there, when two flights of stairs are already available?
At about 28:00 : When Eomer tells Aragorn and his companions about slaying the orcs, he points to a column of smoke rising from an open rocky hill area with no trees in sight. Yet the orc-fight and the pyre are obviously sited at the edge of Fangorn Forest,.
In the final closing shot, the camera rises above Minas Morgul and looks out over Mordor towards Barad-Dûr (the Dark Tower) and Mount Doom. In the shot, Barad-Dûr is to the left of Mount Doom. This is in error; according to Tolkien's maps (which are shown earlier in this film), from that vantage point Barad-Dûr should be slightly to the right of Mount Doom. The shot seen here is repeated from the vantage point of Frodo and Sam's earlier approach at the pass of Morannon, near the Death Marshes.
The face-off between Frodo and the winged Nazgûl is a serious plot hole in the film. The whole point of the quest of the Fellowship was to leave Sauron in doubt about the whereabouts of the Ring, and to distract him from it and its location as it is carried closer to Mordor. That was the only chance for the quest to succeed. As far as he knows the Ring is missing somewhere in the region of the Shire, and nothing leads him to believe otherwise. But putting Frodo directly in front of a Nazgûl in Osgiliath, about to put the Ring on, would alert Sauron to the fact that the Ring not only has been found, but it's in Gondor and is perilously close to his borders. He would have immediately thrown the full weight of all his armies on Gondor to reclaim the Ring and the war would have been lost.
When Faramir's party is called back to Osgiliath, they stop on a ridge looking toward the city. In the distance, you can see Minas Tirith, which is west of Osgiliath; therefore the party is on the eastern side of the Anduin. Once they reach the city, one of the men of Gondor mentions that Mordor's forces have taken the eastern half of the city. So how did Faramir's party get to the western side? If they used the sewer that Faramir sends Frodo and Sam into later, why did he have to explain to them what those sewers were at that time? They'd already have been through them once.
The sub plot of Faramir taking the hobbits to Osgiliath reduces him to no better than his brother. The entire reason for the contrast between the brothers was to show that Faramir was the better man who did not give into the Ring's temptation, least of all for the very petty chance of sucking up to his father. If he had been as weak as Boromir, Aragorn would not have been so quick to make him his Steward when he took the throne.
The Ents refusing to fight in the war is a major plot hole. It ignores the fact that the Ents knew everything that happened within the borders of Fangorn, and that they knew of the orcs' destruction of the southern borders of the forest long before the hobbits had even arrived.
When the Westfold village is being attacked by the Hill Folk there seems to be only one horse in the village; as these are the people of Rohan ("The Horse Lands") we can assume the fighting men & their horses are away but where are the rest of the horses? There should be mares, foals, yearlings, & older horses no longer fit for fighting quite near to the village (there is a corral clearly visible in the village).
Just as Ugluk and the troop of Uruk-Hai stop and Uruk asks, "What is it? What do you smell?" one of the Uruk-Hai fails to notice a bump in the terrain and goes sprawling to the floor.
When Eomer gets on his horse after his first meeting with Aragorn, Gimli and Legolas, you can clearly see his sword slipping out of his scabbard and falling down.
In the extended edition, in the stable at Edoras, Aragorn tells the stable hands to set the horse Brego free. When the horse Brego comes to Aragorn at the riverbank, he is wearing a halter and rope. A good horseman would never leave a halter on a horse when he is loosed into the wild, as it could get hung up on a branch or other obstacle and cause the horse injury. Likewise they would not leave a lead rope dangling off a halter even if turning the horse into a pasture. The lead is so long that it drags between the horse's legs; this would be a hazard.
During the battle of Helm's Deep, Aragorn orders the archers to shoot by yelling 'Fire!'. This command appeared after the introduction of firearms. Earlier, an archer commander would use the command 'Shoot!' or 'Release!'.
When Theoden is discussing the defenses of Helm's Deep with Aragorn it never occurs to either of them that destroying the causeway (or at least part of it) instead of just 'covering it from above' would have gone a long way to prevent the eventual breach of the gates of the Keep.