And Sauron's outside the gates of Minas Tirith in The Return of the King.
The Hobbit: The Desolation of Smaug has Azog's army of Orcs and Wargs marching out of Dol Guldur.
Happens at least once in each of the Star Wars Prequels.
In The Phantom Menace, where battle droids are marching in formation on the Trade Federation Control Ship shortly after the movie begins, and later as they march into battle outside the city on the planet near the film's climax.
In one of the last scenes of Attack of the Clones, where the clone army is shown marching in formation on Coruscant as they depart for war.
In Revenge of the Sith, where a battalion of clone troopers marches into the Jedi Temple, led by Darth Vader.
Jehnna: "Conan! There are six of them against her!" Conan: "One, two, three...I think you're right!"
In Spartacus the disciplined cohorts of a Roman legion appear over the horizon and march down in formation to take up position on the hillside opposite Spartacus's slave army. Then a second legion repeats the process - then a third also marches onto the field.
The Imperial Order in the later Sword of Truth books fields an army that numbers in the millions. To put this in perspective, before they showed up, 100,000 troops was considered a large army.
In The Silmarillion, at the Great Battle of the War of Wrath, Morgoth's army of Orcs, Trolls and Balrogs has grown so large that it fills the entire plain on which the previous battles were fought.
In The Wheel of Time The Dragon Reborn has armies numbering in the hundreds of thousands. In The Path Of Daggers, one character thinks to himself that he can remember when 5000 men was a large army, before the coming of the Dragon. Several scenes describe the tiresome logistics of marching and supply, though that gets (much) easier with the advent of Mass Teleportation.
However, military parades are given very little attention in the series.
Jesus' army of saints at the Battle of Armageddon in the Left Behind book Glorious Appearing. Of course, they're mostly there to praise the Lord while Jesus does all the work of slaying His enemies with the Word Of God.
Also the 200 million horsemen that sweep across the globe during one of God's Trumpet Judgments, looking for those that do not bear the Seal of God on their foreheads to slay.
The Tyrant's army from Chronicles of the Emerged World. Partly justified as 1) the troops are artificially-created soldiers. 2) he has five lands out of eight under his command. From the second book onward, this is brought Up to Eleven as he summon an army made from the ghosts of all those who died in battle.
Ungatt Trunn's Blue Hordes in the Redwall book Lord Brocktree do this when they march, and number enough to be able to intimidate his enemies by causing earthquakes by jumping in sync, making the stars "fall" by lighting torches and concealing the stars in the sky, and making the land "disappear" by standing on it. Of course this is one book where Easy Logistics is averted, the good guys attacking foraging parties in an effort to make them starve. For the most part they succeed, to the point where the "siege" that happens once Brocktree and his allies are in possession of Salamandastron again is more the woodlanders pretending that they're partying it up inside while the Blue Hordes sit and wait for scraps of food to be chucked out the window.
JamieHewlett's music video Monkey Bee is a remix of a song from his Monkey: Journey To The West album. As expected, it is loosely based on Journey to the West. At the end of the video, the Monkey King is faced with a massive amry of the undead, resulting in a Bolivian Army Ending. The video can be seen here.
Warhammer 40,000 Imperial Guard forces are usually shown in this way in their codex books, considering the Imperium of Man is The Empire of a million worlds, the amount of forces marching can literally go up to the horizon.
The Chronicles of Narnia video game battle sequences featured endless swarms of enemies marching past in the background. The developers actually wrote a software app called Battlemarch to produce the effect.
This trope is invoked by the Sligs for an animation test for the canceled Oddworld game, Hand of Odd. Done infront of a picture of a burger.
Invoked in cutscenes of Rise of Legends by both Giacomo and the Doge of Venucci. Clockwork spiders and mechanical soldiers, bonus.
Done at the beginning Gears of War 2, complete with an inspiring speech.
It's not actually an entire army, but when the US task force tries to arrest Liquid Ocelot in Prague in Metal Gear Solid 4, it takes over three minutes for several dozens of trucks, ten patrol boats, six helicopters, and hundreds of soldiers to come out of their hiding spots and surround his boat on the river. But even with just three mooks and himself, Ocelot doesn't think about surrendering. Instead, in a terrible subversion, he already has the master password to shut down all their equipment and when the soldiers are ordered to open fire, nothing happens. Then Ocelot's mooks mow down the entire Task Force in a few moments.
Both Rome and Medieval II of the Total War series end the intro videos for factions with this tropes.
The intro cutscene of Final Fantasy XII features the forces of Dalmasca doing this at one point, with ground troops, cavalry, and transport airships filling the main plaza of Rabanastre in front of the palace.
Happens several times in the Dawn of War series, most often when invading the faction HQ in Dark Crusade and Soulstorm. Especially when the faction is the ImperialGuard.
The opening sequence of Avatar: The Last Airbender contains a shot of a huge crowd of Fire Nation soldiers in front of an armada of ships.
ReBoot's pilot episode has Megabyte's mooks marching across the underground lair. They aren't going anywhere (yet, as they are waiting for Bob to open a portal), but it looks awesome and is meant to intimidate Bob.
Military Parades, most famously, the Red Army. China, India and Russia continue to mount the largest military parades in the world.
Subverted when the communists did their victory parade after taking Saigon, ending the Vietnam War. Having fought mainly as guerrilla fighters the NVA and VC forces had never been trained to march, so they had to do the parade in trucks.
James Oglethorpe used a forest that hid where his army had come from and where it was going, and marched a small army in a circle to make it look much bigger.
Rommel succeeded in pulling off the same "unending loop" trick, without the benefit of forest cover and with tanks.
Improved upon, perhaps by others in the same desert, who used trucks disguised as tanks, tanks disguised as trucks, the truck and tank disguises left behind in the front line where they would be seen, trucks pulling trailers that left the tracks of tanks, fake airfields with fake aircraft (sometimes bombed with fake bombs), fake railroads and railheads 100 miles south of the real railheads, ammo, water and fuel dumps that were sometimes fake covering the real ones. All this constructed to a realistic timetable that indicated an attack several weeks later than the actual attack. Job done. Nazis lose.note The British were known to have employed stage magicians as consultants in creating these ruses, making this a Real Life case of Functional Magic.
The Soviets used this trick with strategic bombers during their military parades in the 1950s, deceiving American observers and creating the myth of the Bomber Gap. Believing their long-range bomber fleet to be massively inferior to the Soviet one, the Americans promptly invested as much as they could in research and production of ICBMs. Yes, much of the Cold War arms race was due to this ploy.
Another classic tactic is to set a lot of fake campfires when your army bunks down for the night, so your forces look much bigger than they really are
This sort of trick has been used in other ways as well. Soldiers in a castle under siege in Austria were purported to have paraded their one cow on the battlements again and again each time painted to look differently. It supposedly worked, convincing the hostile forces outside that the castle had so many resources stocked up that it was pointless to try and starve them out in a siege. It was more of a million moo march though.
Victorious Roman generals would be feted with "triumphs", enormous festivals meant to honour the conquering hero of the Republic. An enormous parade would begin at the Field of Mars, winding its way past shrines while crowds of plebeians roared "Io Triomphe!", before finally reaching the great Temple of Jupiter. The general was followed by his soldiers as well as a host of toga-clad senators and priests, families of prominent patricians, and the Vestal Virgins. Chariots bore the plundered loot of subjugated tribes and captured barbarians were yanked along in chains. The general, at the head of the procession, was followed by a slave who held a laurel wreath over his head while whispering "remember, you are mortal" into his ear. Later, during the Empire, only the Emperor was feted in this manner - whether he had led his troops in the field or not.
The Trooping of the Colour can look suspiciously like this.
This tactic has also been recorded in The Bible - from an initial standing army of 32,000 men, Gideon selected 300 men and used this tactic against a much larger Midianite-Amalek combined force.
The elite fighters of ancient Persia were known as 'the Immortals' not because they were particularly invulnerable, but because the fighting column was so deep as to seem never-ending to their opponents.
Also helped that each individual dressed the same (and covered most of their body) and all generally acted stoically before battle, meaning if one did actually fall another would take its place the next time they got in formation and it would appear to be the same guy.