The second game in the Halo series, released in 2004; it is the highest-selling game for the original XBox.Following the events of the first game, Master Chief arrives back at Earth, praised as a hero. In the midst of celebration, a Covenant attack begins on Earth, and Master Chief races to stop them. He learns that the Covenant are looking for something on Earth, and his quest takes him to a new Halo ring, where he explores more of the mystery behind The Flood.The major change from the first Halo game is that the campaign is told from two different angles: that of Master Chief, and that of a member of the Covenant, a soldier in the Elite Mook race from the first game (the actual character is introduced in this game). He is known only as the Arbiter, and he was originally the leader of the Covenant forces that encountered Master Chief on the first Halo ring. Disgraced by the Covenant leaders due to his failure to stop the ring's destruction, the Arbiter is given a suicide mission that may potentially help him reclaim some of his lost honor. As the Arbiter learns more about the origin of the Halo rings and fate of the Forerunners, he eventually comes to doubt the Covenant cause...On the gameplay side, Halo 2 introduced Dual Wielding with a class of weapons you can pair off with any other type in the same class (this is portrayed as something only Master Chief, Covenant Elites, and Covenant Brutes can do). It also featured vehicle hijacking - assuming you could get close enough to the vehicle without being gunned down or run over. Halo 2 solidified the presence of online console gaming thanks to the original XBox Live service; thanks to Halo 2's success, practically any game of nearly any genre will have at least some debate from the developers on whether or not it should feature an online component.
Lord Hood: Master Chief, you mind explaining what you're doing on that ship? Master Chief: Sir, finishing this fight.
Big Bulky Bomb: The Covenant boarding parties bring one onto Cairo station, and a suicide-squad of Elite Zealots guard it while waiting for it to detonate. The thing is easily bigger than any one of them or the Master Chief, and is covered in spikes.
Boring but Practical: The Battle Rifle, a normal, burst fire human rifle with a 2x scope. It kills Grunts and Jackals with one headshot burst, even on Legendary, and when usde in combination with the plasma pistol is also capable of absolutely destroying Elites. It can also allow you to out snipe Jackals and the ammo for it is usually plentiful.
Cliff Hanger: The story ends with one of the most infamous cliffhangers in all of videogaming, being a very obvious Sequel Hook rather than actual completion of the main threats a'la the first game.
Cortana: Ask yourself this question: "Is what I'm doing right now helping Cortana keep this station from exploding into tiny, tiny bits?"
Death Seeker: The Arbiter. Pretty much comes with the job description.
Determinator: Meta example. The only thing that ended Halo 2's online gaming scene was the original Xbox Live servers getting shut down. The game was launched on Nov 9th, 2004, and the servers officially shut down on Apr 15, 2010. Officially, that is; several players hung on until getting booted on May 11th.
Dual Wielding: The first game to have a set of weapons that you can randomly pair with other designated one-handed weapons.
Early-Bird Cameo: An example map in the PC port includes a version of the SMG with a slightly-smaller magazine and a suppressor. This silenced SMG returned in Halo 3: ODST as the primary weapon of the titular ODST squad.
Enemy Civil War: Following the assassination of the Prophet of Regret, the Elites are stripped of their traditional role as honor guards to the Prophets, which is given to the Brutes. The Elites do not take kindly to this, and end up seceding from the Covenant, along with several individuals of other species.
Enemy Mine: The Gravemind recruits Master Chief and the Arbiter, making it a three way enemy mine.
Also, Sergeant Johnson, Miranda Keyes allying with the Elites (especially the Arbiter) and two Hunters.
Fire Keeps It Dead: When the Flood turn up one of the Arbiter's fellow Sangheili laments that they didn't bring anything to burn the bodies with.
Hey, It's That Voice!: Orlando Jones("That thing is really starting to piss me off!), Michelle Rodriguez("It blew right through us! Rockets, .50 cal, they didn't do a thing!"), David Cross and John Kassir (aka The Crypt Keeper) were varous Marines.
Hoist by His Own Petard: After the Chief deactivates the antimatter bomb on board Cairo Station, he proceeds to take it down to a hangar, open the doors, and use the decompression to hurl the bomb toward a Covenant carrier. But wait, that's not all! He grabs hold of the bomb so that he can activate it right inside the carrier's reactor, before jumping off again and landing on a passing frigate.
Master Chief: Sir, permission to leave the station?
Justified Tutorial: Master Chief gets an upgraded armor system (Mjolnir Mark VI) that gives an In-Universe explanation for some of the gameplay changes (no more need for health packs, supposedly there is an internal "bio foam" system). As well, the technicians have him look around to get adjusted to the new armor.
Made of Explodium: Covenant vehicles in this game, more so than the other games. Do enough damage and they violently explode. Twice.
Neo-Africa: New Mombasa, Kenya is a high tech city and spaceport. At least, when the game begins.
Never Trust a Trailer: The trailers, promotional materials and even the blurb on the game's box all gave the impression that the Chief would spend all or most of the game helping humanity repel the Covenant invasion on Earth.
Old Shame: Some of the devs don't like how the single player campaign turned out, if the term "disastrous flaming turd of failure" is an expression of regret.
Which makes the fact that it's the only Halo game not on Xbox Live not that hard to understand.
Optional Stealth: The Arbiter's Invisibility Cloak lasts for only about five seconds anyway, so ignoring it is perfectly viable option if you don't like having to wear down all your enemies versus getting one free assassination. A bonus item lets Master Chief have invisibility too, but it lasts for the same amount of time and the second disadvantage of no visible timer.
Retcon: Master Chief (with Cortana) was the only human to survive the destruction of the first Halo. The Legendary ending of the first game even gave a (humorous non-canon) scene depicting Johnson's last moments before the Autumn exploded. This game just has him show up in the medal ceremony with no explanation given. Halo: First Strike had to explain how he survived.
Mst. Sgt. Gunns: So, Johnson, when you gonna tell me how you made it back home in one piece? Sgt. Johnson: Sorry Gunns, it's classified. Mst. Sgt. Gunns:My ass! Well you can forget about those adjustments to your A2 scope, and...(continues shouting as Johnson and Chief move out of earshot)
Right Hand Versus Left Hand: The Covenant infighting between the Brutes and the Elites leads to a schism in the Covenant and basically the only hope for Humanity's survival.
Sequel Hook: Also one of the most infamous ones in video game history.
The Missingno.: The Gravemind mission has the "Honor Guard Councillor", a Zealot (gold) elite that was accidentally programmed to have a "dogmatic" voice/personality; since the level has no permutation data for dogmatic Elites, it defaults to Honor Guard armor and Ultra palette, with randomly chosen head types(most frequently the Councillor, hence the nickname).
This Cannot Be!: In the final mission, when the presumed dead Arbiter returns to confront Tartarus.
Tartarus:(gasps and jerks his neck up in surprise) Impossible!
Took a Level in Badass: The generic UNSC Marines got way more competent since Halo 2. They're more accurate, they have twice as much health, and they can drive vehicles. They're actually pretty helpful when they appear as long as you throw any submachine guns and shotguns you find in the trash and replace them with Battle Rifles and Sniper Rifles. Give one a rocket launcher and the marine's good aim and unlimited ammo will usually let him rack up almost as many kills as you.
Trailers Always Lie: The E3 demo (and the advertising, and the boxart) gave the impression that the game would be set on Earth's surface. The final game had a grand total of two levels set there.
In a more straight version of the trope, the "Give them back their bomb" sequence in the trailer has Earth in much more trouble than in the actual game, in which the Covenant barely stick around for. Earth's on fire? Not really. Save that for the next game and ODST.
Translator Microbes: Cortana, being an advanced A.I., can understand the Prophets language. And she can translate it for others to hear.
Prophet of Regret message:*speaking alien language*
Forerunner Tank was a level that was cut from the game very early in development. That said, it gained the above trope because of what the developers said about it: "Awesomeness would ensue."
Not to mention the demo of the game. It appears that everything they had in the demo that wasn't used in Halo 2, was used to make an entirely new game; Halo 3: ODST.
You Have Failed Me / You Have Outlived Your Usefulness: The Prophets decided to scapegoat Thel for the destruction of the Halo ring. They soon made him an Arbiter to retrieve, Guilty Spark 343, and the key to the second Halo. After succeeding in both, Tartarus could now kill him under the Prophets orders. After that, the Covenant decided to turn on the entire Elites in favor of the Brutes. But the Elites are much better warriors than all of them combine, that they turn against the Covenant.