Land Sea Sky: The three largest armies can be seen to represent this in their favoured forms of warfare. The krogans utilise a ground-based Army and Tanks (Land), the humans use a Space-Navy with many Carriers to quickly deploy Marine forces (Sea), while the turians provide aerial-support and bombing runs (Sky).
Adrenaline Rush does not take you into Bullet Time for the multiplayer, but it still instantly reloads your weapon.
Tactical Cloak can be used to keep your overloaded Infiltrator competitive. Since Cloak has a proportional cooldown now (always 3 seconds if you break it immediately), using powers like Energy Drain or Sabotage is much more efficient if you cloak first. Cloak's cooldown will override the used power's cooldown, shaving the time right off.
Tapping the context-sensitive "use" button (the one that activates, sprints, enters cover, etc) at just the right moment will cancel the reload animation, especially when standing still. If done right after the weapon magazine actually replenishes, the weapon can be fired immediately.
Lampshade Hanging: Generally all over the place, but Shepard gets a nice dig in when s/he expresses mild jealousy about the geth believing Legion's warning's about the Reapers.
A particularly excellent example comes from stalker and wannabe hero Conrad Verner, who is surprised when he finds out that they've replaced the old cooling systems from the original Mass Effect with a thermal clip system, pointing out that they might as well go back to ordinary ammunition. He even asks if the guns can, at least, still cool down on their own, and Shepard (rather uncomfortably) admits that they removed the self-cooling systems in order to make space for the clips. Every player probably asked the same thing, but Shepard blows him off.
It's also sort of a Call Back to the first game, in which Geth Snipers did the same thing (because they were using the Assassination power, which buffed sniper damage and accuracy for the next shot). Thankfully, it's not a One-Hit Kill in this game.
Reaper Ravagers also have a sort of targeting laser... two, in fact. The purpose is the same.
Last Chance Hit Point: Present in both single-player and multiplayer for some attacks—most enemy attacks that break your shields do not overflow into health damage, and if one of those attacks would deplete your health meter, it reduces you to a mere fraction of your last health bar and gives you a very brief invulnerability window.
Jacob mentions that his girlfriend wants to name their baby after Shepard... as in, naming the kid Shepard. He intends to talk her out of it, though. Later, he'll mention that his girlfriend thinks that "Hackett" is a good name... for their baby girl.
Carried through even to include the plaque placed on the Normandy memorial in the ending, even though it's text (and thus maybe the one place it could have been averted.)
Shepard will have the opportunity to bed his/her love interest (even if it's a new romance) right before the point of no return.
Provided they survived ME2, and you pardoned them in the Citadel Spectre office, Ken and Gabby finally admit their love for each other if you go visit them at the very bottom of Engineering prior to the final mission. This can happen way earlier though.
If you didn't romance either of them, Garrus and Tali are seen embracing when you walk in on them at the forward batteries. Tali says in the conversation afterwards (likely half-joking) that "This is just a fling, Vakarian. I'm only using you for your body."
The kid in the beginning that says "You can't help me." and dies shortly thereafter regardless of what you do seems to be talking to the player that you cannot save everyone.
A scene that follows continues this, with Shepard having the option to express just that.
Shepard: It's hard enough fighting a war, but it's worse knowing no matter how hard you try, you can't save them all.
Conrad references the save import bug from the second game, apologising for claiming that Shepard held a gun to his face when they never did so, he thinks he was under a bit of stress at the time.
EDI at one point speculates that reality is in fact a holographic projection onto a 2-dimensional surface, but no one is capable of sensing reality in this way, not even the Reapers.
In Leviathan, EDI references online games having to nerf characters, weapons and enemies, after players complain they were too overpowered. The multiplayer has had this occur several times to make Infiltrators and Vanguards builds less gamebreaking, and this is frequent criticism leveled against enemies such as Banshees.
In Citadel, most of the conversations between random soldiers on the Silversun Strip refer to various aspects of the multiplayer.
Just before the Citadel DLC mission in which Shepard retakes the Normandy, after the player chooses two squad members to accompany Shepard, afterward one of the unchosen characters will express disappointment at not being picked ... and if there happens to be a character who the player never chooses, he/she will note this.
The final scene of the Citadel DLC is one that works in-universe, but also feels like BioWare and the voice actors saying goodbye to the trilogy and characters.
Squad Member: It's been a good ride.
Shepard: The best.
Legion of Lost Souls: In a manner with the squads in multiplayer. They are ostensibly Systems Alliance units and operate under Alliance command, with most of their members being human soldiers and other military specialists, but they also include volunteers and mercenaries from a variety of other races, such as turians, asari, krogan, drell, and quarians. Now with the Resurgence/Rebellion/Retaliation/Reckoning DLC Packs, geth, batarians, vorcha, Cerberus defectors, volus and Leviathan-liberated Collectors join the party.
Let's Get Dangerous: In the Retaliation DLC, you get to be a volus. Played right, and you're capable of keeping up with half-ton, headbutting murder-lizards and people who can crush other people with their minds (though as a Volus biotic, you'd be the type to crush people with your mind).
Lighter and Softer: The CitadelDLC can feel a tad jarring at points due to how dark the main game is, especially since, in order to maximize the number of available characters it's meant to be played just before the endgame missions begin. It's intentionally goofy, fun, filled with character comedy and ends on a party for all of the squad members in the series. Tropes Are Tools though as it's meant to be the final sendoff to the trilogy and the cast of characters and thus is technically intended to be played by those who have already played through the game a few times (and, even more specifically, have played through the complete trilogy).
What krogan characters get in multi-player after killing three enemies in close succession with melee attacks. What exact bonuses are given depends on your progression.
The vorcha Bloodlust ability works the same way, with successive kills granting bonuses to health regeneration, movement speed and damage.
Limited Loadout: Shepard can take one of each weapon from five types, with a slot for each on his/her back. Restricting this, the game implemented a "weight" system for weapons where every gun slows down the rate at which powers recharge. Technically, any class can carry five guns at any time but doing so turns your recharge rate into molasses. Party members get two guns at a time. Multiplayer also uses the weight system but with two slots.
Linear Warriors, Quadratic Wizards: Surprisingly inverted with classes in multiplayer. Classes can generally be divided into ones which primarily rely on their active-use powers to deal damage (the wizards) and classes that rely on their weapons to deal damage (the warriors.) In early progression, a player's stock of weapons and weapon mods will be very limited and will have a hard time competing with, while they can level up a class quickly, relying mostly on their active-use powers for their primary damage. However, as players unlock more item packs, weapons will gradually improve in quality and level, rapidly catching up to and even exceeding the active-use powers for damage.
As a more specific example in multiplayer, any enhancements (via weapon mods, power evolutions, and gear) to melee damage are multiplicative, while enhancements to ability damage are additive. Technically both are linear, but a given amount of enhancement to the former will generate a much greater effect than the same degree of enhancement to the later. In that sense, melee fighters out-damage casters, given the same level of optimization.
Living Relic: Javik, the Prothean party member made available in the From Ashes DLC who slept from the previous cycle in a stasis pod. To him, the most advanced races in the galaxy are but primitive barbarians and, in the case of the salarians, a food source (their liver is preferably served raw as a delicacy). He is ignorant of our culture, society and history, and views our philosophy and religions with near contempt, but also sees in us the potential for ending the Reaper cycle and vengeance for the slaughtered Prothean empire.
Single player has a load screen between each level of the Normandy and each individual section of the Citadel.
In multiplayer it is possible to invite a friend to a game, have him accept, switch the game to public and have it fill up before he can join.
London Town: London (and UK Alliance Headquarters) is hit several moments before the attack on the Vancouver-Seattle Megapolis, with the first trailer showing no less than eight Reapers walking all over it. It is where Shepard and Anderson make their final push on Earth.
Lonely Piano Piece: The end of the introductory sequence culminates in a slow tune ("Leaving Earth") which is repeated numerous times throughout the game.
Completing Priority: Tuchanka will make many side quests on the Citadel impossible to complete. There is little to no indication of this in the game. See Point of No Return.
While most upgrades, weapons or sidequest objectives will become available for purchase if you missed them during gameplay (upgrades and weapons at the various stores, objectives at the Spectre Requisitions terminal), the Shuriken SMG, Katana shotgun, Mantis sniper riflenote Shepard automatically receives one of these three weapons at the beginning of the second mission based on class, and Talon pistol and Saber assault rifle do not.
Lost Superweapon: The Crucible, an ancient anti-Reaper superweapon discovered in the Mars Prothean Archives at the beginning of the game. The kicker is that the cast initially assume it is of Prothean origin, only to learn it has been designed bit-by-bit over multiple extinction cycles.
Love Theme: "I Was Lost Without You", a more melancholy sounding tune than the previous two.
Luck-Based Mission: Multiplayer objectives can frequently be this. Sometimes you score and all the various items you need to activate/deactivate are placed in the same room and far from the enemies, other times you have to kill four Banshees which all are heavily guarded by their Reaper allies.
Cerberus Guardians carry riot shields into battle. They are quite effective at soaking up damage; however, the shields can be worked around with good tactics, good aim, or good use of powers. Alternatively, if you have a big enough gun or equip armor-piercing mods, they can be flat out ignored.
Luke, I Am Your Father: Having been heavily implied in Mass Effect 2, this game confirms that Matriarch Aethyta is Liara's "father."
Macross Missile Massacre: The Hydra missile launcher, which is occasionally encountered in single player. Instead of firing one big missile, it fires a volley of self-guided ones with three-stage explosives, making it equally useful for taking out bosses or swarms of standard Mooks.
Match Maker Quest: Shepard can encourage EDI and Joker to become a couple and can do the same for Ken and Gabby. The CitadelDLC gives Shepard the opportunity to encourage Ashley and Vega to hook up, and as a downplayed example Shepard can be a wingman to Garrus at a casino bar.
McNinja: Cerberus Phantoms. Also, drell characters from multi-player 'roll' like ninjas and get a speed bonus, and the N7 Slayer gets a strange ninja/trenchcoat design, complete with Asian-esque sword - which makes sense since they use Kai Leng's meshes.
If Miranda survived the previous game, she will return and be searching for her missing sister. Shepard will caution her to be careful, to which she will respond "No promises." If you contact her before the final charge on Earth, they flip it around.
Mordin gives us two of these. In the previous game he told Shepard he sometimes fantasized that it wasn't his responsibility to work on the genophage that keeps krogan population in check. He follows this up by calling it a fool's wish because "It had to be me. Someone else might have gotten it wrong." Later, as Mordin prepares ascends to the top of a collapsing tower to make certain the cure for the genophage is effective, he repeats this line, though this time without any regrets as to his course of action.
Shepard and Legion have a flip where Shepard wishes Legion "Good luck" and he responds "Acknowledged". They repeat it with the roles reversed near the end of the mission.
One from all the way back from the first game makes itself known here; during a conversation with EDI, Shepard can find him/herself echoing one of Saren's last words, with the opposite intended effect:
Are you telling me that submission is preferable to extinction?
Dr. Eva Coré. In Mass Effect: Evolution, it was the name of one of Jack Harper's companions. Who is Jack Harper? The Illusive Man.
The second-in-command of the Eclipse mercenary organization, who is a more subdued mercenary than the violently psychotic leader Jona Sederis, is named Sayn.
Mechanical Evolution: Discussed by Shepard regarding the evolution of the geth species. Legion and the geth can evolve to achieve sentience far beyond their original programming parameters.
Medium Blending: When reports start coming in about the Reaper invasion, it is shown with live-action footage from one of the trailers.
Mega City: The story starts in a city that is described as Vancouver, British Columbia; Seattle, Washington; and Portland, Oregon merged. Later references make it clear that you were in the "Vancouver" part.
Meta Casting: Buzz Aldrin, the second man on the moon, voices a space-focused grandfather in the post-credits scene.
Mighty Glacier: Krogan multi-player characters, who have much less agility than the other races but have far higher HP, Shields, and resistance to damage.
Similarly, batarian characters, and N7 Destoyers, whose suits incorporate a missile launcher.
The entire concept behind the N7 Paladin. While the slowest and least agile of the all of the human characters, it has massive shield and health points along with a durable Omni-shield that can be used to asorb a great deal of fire.
Krogan Warlords deserve a particular mention, since their size makes it impossible for Husks or Abominations to grab them. On top of that, they are Mighty Glaciers among Krogans, and can regenerate their health.
But the Mightiest and Glacier-iest of all the characters arrived in the Geth Juggernaut, who is the size of a Geth Prime, immune to Sync-Kills and unable to walk faster than a purposeful stroll.
Mildly Military: Discussed if you have Ken and Gabby rejoin the crew. Engineer Adams, who unlike Ken and Gabby did not leave the Alliance to enlist with Cerberus, will praise both of their skills, but he will comment that Ken needs to learn to keep his mouth shut, and that he needs to remind Ken about proper military procedure and the chain of command.
Mind Screwdriver: Minor example, but Mass Effect 3 finally clears up the mystery surrounding Keiji's greybox in Kasumi's loyalty mission, answering what information could be so important that it could start a war if it got out: the information is about a "black ops" raid that the Alliance conducted on the batarians. That could have started a war if the batarians had found out about it.
Mini Game Zone: The Silversun Strip from the "Citadel" DLC. It has an arena, an arcade, a casino and a customizable apartment. And dozens of opportunities to interact with squadmates.
Mini Mecha: Cerberus has ten-foot tall mecha at their disposal. You can actually kill the pilot before destroying the mech, letting Shepard run rampant in one.
Mobile Factory: The Volus Fabrication Units (discovered by scanning a planet in the Aethon Cluster) can be used to replicate custom plastic parts for the Crucible using mobile production platforms.
Modular Epilogue: The game didn't have one of these originally as it presented the consequences of your choices during the game itself, but with the Extended Cut DLC, the scene for the ending you chose is followed by slides of what various races and squadmates are up to, depending on who survived and certain choices you made earlier in the game.
How Cerberus must have found out about the krogan female on Sur'Kesh.
Garrus: Cerberus must have been tipped off. They got here too fast. Liara: Every war has its traitors.
Mordin/Padok was Wrex's mole — he leaked info about the fertile females and encouraged political pressure to release them. He is not Wrex's only source, however, as you will learn the hard way if you betray him.
Monumental Damage: In the trailer we can see a pretty busted up Big Ben Clocktower, and a Reaper just about to land on the London Eye. The tower does, however, manage to remain standing through the end of the game.
Mood Whiplash: The entire Citadel DLC. Especially when going for 100% completion, it will be played right between the Sanctuary, where unspeakable experiments are conducted, and Thessia, where an entire planet and its population get killed before it and the climactic final fight after it. Yet it provides lighthearted banter galore and is almost completely upbeat.
Mooks but No Bosses: Especially jarring since the previous games had several bosses. There's only one traditional boss in the entire game, and he's just a slightly different version of a fairly common Elite Mook with more health. The other "boss fights" consist of the Reapers on Tuchanka and Earth (who are merely environmental hazards that aren't directly fought), the Reaper on Rannoch, and Eva Core (the latter two are more like quick time events/interactable cutscenes).
Finally averted in the Citadel DLC, which has Shepard's clone as the boss.
The Revenant Machine Gun can pump out the dakka with seven 60 round clips. (The Geth Pulse Rifle [80 rounds], Geth Plasma SMG and Prothean Particle Beam [both 100 rounds] - but these come off more as Beam Spam than Dakka.) That's before you apply the Thermal Clip Extension V mod giving it an 80% increase bringing it up to 108 rounds per clip.
The Marksman ability turns ANY automatic weapon you are holding into this by cranking your rate-of-fire Up to Eleven. The N7 Destroyer's Devastator Mode increases rate of fire and magazine size.
Found, of all places, in a submachine gun. The Geth Plasma SMG spins a disk of plasma and then flings off bolts from the spinning disk, steadily increasing rate of fire to an absurd level. If loaded with the right weapon mods, it can sustain its frighteningly accurate huge volume of fire for a very long time. The flavor text for it reveals that it's a pint-sized version of a much larger Geth weapon, the heavy Spitfire. It is the smallest bullet hose you will ever see.
Multiplayer eventually got the N7 Typhoon, which is pretty much a cross between the Revenant and the Geth SMG... plus armor-piercing ability and extra damage against shields and barriers. With only a minor spinup to hinder it, it had to be nerfed the day after it was released because the piercing was just too good; the aforementioned N7 Destroyer with one of these babies was virtually unstoppable against armored enemies. The Typhoon's main issue being its enormous recoil limiting its effective range, the flavor text (and mechanical performance) suggesting this is because it is practically a cut-down assault rifle, with all the power that implies but much less stabilization.
See also the Piranha shotgun, which is to the Scimitar what the Typhoon is to the Revenant.
The Geth Spitfire minigun (which is a single-use heavy weapon in campaign) has been added to multiplayer as a machine gun. It can spit out more damage than the Typhoon, but it's heavier.
Motivational Kiss: When EDI describes Normandy's readiness before the final battle, she states she even kissed Joker for luck.
Motivational Lie: After the fall of Thessia, if you use the Paragon interrupt during the Liara/Javik confrontation, Javik explains that the Protheans believed that the asari were the best hope for this cycle, and that the Protheans protected and nurtured them because they saw their potential. After Liara leaves, Shepard asks whether Javik meant what he said; he asks "does it matter?" and you get as an addendum either "I will tell you what you want to hear: I meant what I said", "She believes it. So she will keep fighting."
Multiple Endings: Comes in three final options; which options are available and the aftermath of the Crucible's activation is determined by your Effective Military Strength.
Control: Shepard uses the Illusive Man's plan and takes control of the Reapers, ordering them to cease hostilities and leave. In the Extended Cut, it is revealed that Shepard became the Reapers, all of them, and is rebuilding what they destroyed, vowing to serve as the preserver of all civilization. More renegade Shepards will vow to be a strong leader.
The Extended Cut DLC adds a new ending: Refusal: Shepard decides to reject all of these previous options and essentially tells the Catalyst to go screw himself. Unfortunately, this causes the Catalyst to shut down the Crucible, ruining any chance of defeating the Reapers... in this cycle, at least.
Mundane Luxury: In the monastery for secluded Ardat-Yakshi, you can find a message from one of the inhabitants mentioning that somebody managed to smuggle in a copy of the vid Vaenia. She is arranging a group watching and is practically bursting with anticipation, and all the Asari are risking rather extensive privilege restrictions if they are caught. Dialogue in Mass Effect 2 revealed that Vaenia is a story featuring two asari in love; they are going to these lengths to watch a romance film.
My God, What Have I Done?: If Shepard shoots Mordin before he rides up the elevator to the Shroud, Shepard stands in shock for a moment before turning away with a grimace and throwing the gun away as he/she walks off. Especially significant if it's a Carnifex, the model of pistol he gave you as a good faith gesture the first time you met.
Nail 'Em: The Kishock Harpoon Gun, which will pin enemies to walls if its projectiles are charged enough.
Naval Blockade: Cerberus does this a couple of times, once at the Grissom Academy with a cruiser and a force of fighters, and another around Omega with a force of larger ships after usurping Aria T'Loak.
Neck Lift: Legion will do this to Shepard if you let the quarians wipe out the geth.
Nerf: Two flavors! A lot of guns were changed from the second game:
Now a vanilla weapon, the Phalanx Pistol went from a Hand Cannon that outdid the previous Hand Cannon with 1.5x more damage to being an intermediate between it and the basic pistol; essentially becoming a ".45 ACP" to the Predator's "9mm". The previous Hand Cannon, along with its new variant, is now practically a Sniper Pistol.
The Mattock still retains its power, but now has a max fire rate cap. Fortunately, the Raptor sniper rifle effectively fills its former niche.
The Viper Sniper now only holds half the shots and limits the rate of fire, the trade-off being a significant damage increase. The niche of "rapid-fire sniper" is once again filled by the Raptor.
The Locust SMG got a major damage nerf and is one of the heaviest SMGs.
The Revenant took a 20-shot clip reduction, lost some accuracy and is slightly weaker per shot. Firing on the move also slows you down, regardless of whether you're aiming down the sights.
BioWare also takes a look at the multiplayer every week and adjusts the guns and abilities to balance things out:
The Falcon is probably the most different between modes; its multiplayer fire rate is half that of the campaign version, and its damage was cut as well. Other guns like the Paladin have had their clip sizes adjusted.
Stasis had its cooldown almost doubled, and Sabotage can't hack more than one enemy anymore. Decoy and drone abilities also distract fewer enemies.
Tactical Cloak, the Krysae Rifle and the geth characters' Hunter Mode were all nerfed to combat the proliferation of various Infiltrators. Cloak got hit the hardest, losing half its duration and a third of its damage buffs.
Neutral No Longer: The entire point of the game: sending Shepard out to the various species of the galaxy in order to convince them that focusing solely on their own territories isn't going to work anymore, that they need to unite in order to survive.
Taken literally with the dialogue options, sort of. Almost all dialogues only give two reply choices outside of the Charm/Intimidate persuasion options.
Taken Up to Elevenwith the Leviathan DLC - Shepard gets the race that created the Catalyst, and by extension the reapers themselves, to join the fight!
They get stabbed with disturbing frequency though. Annoyingly, in the Citadel DLC mission, not even Wrex is immune to this. Which counts as Gameplay and Story Segregation, since Krogan are supposed to have extra sets of every possible organs just in case.
New Game+: You'll restart the game at your current level with all your weapons and attachments, the max upgrades for weapons will rise from 5 to 10, and you will get an achievement. However, you will lack credits, Intel Terminal upgrades (with the exception of the Predak Paddlefish intel which can only be obtained in a New Game Plus), and War Assets.
N.G.O. Superpower: Cerberus has been upgraded to a fully-realized military force in this game, with its own fleets of cruisers and fighters, and enough military force to challenge the Systems Alliance throughout its colonies. It also manages to launch a full-scale assault on the Citadel and come close to assassinating the Council, but Shepard afterwards remarks that that was probably the bulk of their total forces, and they would not be able to do anything of the like again.
Nice Job Breaking It, Hero: Some of your choices throughout the trilogy and this game will catch up to you, and not always in a good way. Some specific examples:
If you recruit them in a save where the rachni queen was killed, then her Suspiciously Similar Substitute is revealed to be indoctrinated, and goes on an offscreen rampage through Crucible R&D, causing significant damage to your war assets before she is put down.
If you encourage Javik to embrace the memories of the Echo Shard, the reminder of his lost comrades pushes him into full Death Seeker territory. Otherwise, he will at least be willing to find out what peace looks like if he survives.
On the Citadel, Shepard can overhear two conversations; one between an asari commando with PTSD and an asari psychiatrist in the Huerta Memorial Hospital, one between an Alliance engineer and her sergeant in the D24 docking bay. By listening to the conversations in their entirety, Shepard gets the choice to authorise giving the asari commando a gun and to authorise transferring the Alliance engineer to anti-Reaper missions instead of the anti-Cerberus missions she is supposed to be going on. If you authorise the asari getting a weapon, she commits suicide, reducing the Citadel Defense Force war asset due to traumatizing the doctors and nurses. If you authorize the transfer, then the Alliance war asset is reduced due to "lack of engineers impairing anti-Cerberus missions".
Worse in the second case, even if you authorize the transfer, the engineer and their superior still go through the whole scene with the briefing and all again. Should make them leave the hallway. If you looked at consoles in the early Cerberus lab mission with the Reaper tech, you find her brother's log notes, before and after indoctrination. You probably killed him there, but, even if you didn't, his personality is long gone.
Nightmare Sequence: Occurs several times throughout the game as a way for Shepard to actualize his/her guilt over leaving so many people behind on Earth during the evacuation.
The Infiltrators, if built right, are quite capable of dishing out headshots, launching grenades or performing stealth assassinations with the omniblade while remaining invisible for nearly the entire time. Coupled with a short cooldown for the Tactical Cloak, they can become virtually unstoppable on the battlefield.
The Phantom now has a playable counterpart in the N7 Shadow, who has a sword, Kasumi's Shadow Strike and an devastating Sword Beam attack. For when Infiltrators simply aren't ninja enough!
...and the N7 slayer, a Vanguard who shares sword and biotic abilities with the Phantom. He is also able to teleport at short range, which brings some more ninja points.
No Cutscene Inventory Inertia: In cutscenes, the squad will often be holding either an unmodified M8 Avenger assault rifle or M-3 Predator pistol regardless of whether or not they were carrying those weapons. Sometimes their currently-equipped weapons will also appear on their back/hip in carrying mode, but other times they will completely disappear. Especially jarring if (though to a lesser extent than in Mass Effect 2) you aren't even carrying an assault rifle, and in fact haven't used one all game.
Especially painful when it happens to squadmates that are unable to use Assault Rifles in the last two games, Tali or Liara for example.
A few cutscenes avert this — partially. Characters will have the weapon they were last holding, but will still fire as if they were holding an M8 Avenger, even if they were holding, say, a Widow or a Spike Thrower. In which case, those cutscenes will get loud.
No-Holds-Barred Beatdown: Happens to the Virmire survivor early in the first act (causing them to be out of commission for the rest of the first act), then later to Shepard in the climax.
No Indoor Voice: Batarians, krogan, and vorcha in MP. Everyone else, too, to a lesser extent.
Taking too long to start targeting the Reaper on Rannoch will cause it to devastate the quarian fleet, leading to a Critical Mission Failure.
Early in the assault on Cerberus Headquarters, the bad guys will try to vent the fighter launch bay into space. If you don't find a console to override the venting command in time, Critical Mission Failure.
In the endgame, if you do not drive the Illusive Man to suicide and you do not take either of the two Renegade Interrupt prompts, he shoots you and you die.
If you take too long to choose an ending, "The Crucible has been destroyed" appears on screen, offering you the usual game over options.
Even the Galaxy Map isn't safe. If you are scanning for resources and the Reapers detect you they will chase you around the system until you jump to another. If they catch you then it's game over.
Not so Fast, Bucko!: As Shepard, you land in London and go to work destroying a Reaper anti-aircraft canon. A little while later, the Hammer forces mobilize toward the beam, fighting their way toward an artillery battery to take down a reaper guarding it. The guidance system fails, so you hold your position with your squad while EDI reprograms the guidance system. You are hit by Marauders, Cannibals, Brutes and Banshees. But you hold the line and then fire the remaining missiles and the Reapers goes down. And then Harbinger descends, and your dwindling forces make a dash for the beam, getting fired upon as they do. You are momentarily taken out, but you recover, and badly wounded, you limp toward the beam. Three husks come after you, but you don't let them stop you. A Marauder ambushes you, but you've come too far to be taken out. You drop just close enough, and you're transported to the Citadel. You recover surrounded by dead bodies, but at least someone else made it through. Admiral Anderson is elsewhere, tying to unlock the Citadel. As soon as you find him, you are beset upon by the Illusive Man, now with the power to control your physical actions. You try to reason with him, and maybe you succeed, but not before getting you to shoot Anderson in the gut, maybe not even before he can finish him himself, but one way or the other, the Illusive Man goes down. You stagger to the console and open up the arms, you slump down nearby, and maybe you have a moment of peace with Anderson, and talk about the future to come before he succumbs to his injuries. Maybe you're close to that, yourself, but you have no regrets, as you finally did it, and think it's over. It's not.
No Points for Neutrality: Averted for the first time in the series; paragon and renegade choices, as well as other neutral actions, all stack into a single reputation meter. So, instead of determining which persuasion options are available, the meter determines if you've got a big enough reputation to persuade them. At that point, the actual persuasion can go down any way you want.
No Sell: Humanoid enemies can roll to negate a power's effects. The N7 Destroyer also cannot be staggered by enemy attacks, no matter how powerful they are.
Almost every planet you have visited in the previous two games, you either re-visit or can procure Assets from. Yes, that includes ALL the UNC missions in the Mako from the first game except for Luna (for obvious reasons).
Firebase White, which takes place on Noveria, an area that hasn't been visited since the first game.
The Retaliation DLC pack is a variation on this, adding Collectors to the enemy list for multiplayer.
The last mission of the Omega DLC takes you to the Gozu District, where you recruited Mordin in the previous game and the final fight takes place in Afterlife, Aria's old headquarters.
Not in Front of the Kid: In order to maintain the professionalism Grissom Academy expects of its teachers, Jack has agreed not to swear. Joker asks if she has a Swear Jar, because emptying that could fund a cruiser!
Not Quite The Right Thing: In an unusual variation of this trope, exactly which decisions are Not Quite The Right Thing are different depending on decisions you made in previous games. Some examples:
If Wrex is the Urdnot leader because you were able to get him to see reason on Virmire, then leaving the genophage cure sabotaged is this trope, since Wrex gets tipped off about your betrayal because of an additional STG source, and before you're forced to kill him he takes away hundreds and hundreds of krogan War Assets! But if Wreav is the Urdnot leader because you either killed Wrex on Virmire or never recruited him in the first place, then curing the genophage is this trope, since in the Extended Cut ending, Wreav gathers a huge army of genophage-cured krogan to conquer the galaxy, just as he threatened he would!
In the previous game, rewriting the geth heretics is not quite the right thing if you're trying to broker peace between geth and quarians, although peace is still technically possible with rewritten heretics but much more difficult to pull off; and it's also not quite the right thing if you want to kill off the geth and keep the quarians, since rewriting the geth heretics results in weaker Quarian War Assets. But it is the right thing if you want to kill off the quarians and keep the geth because rewriting the geth heretics and then killing the quarians means you get much stronger Geth War Assets. Likewise, destroying the geth heretics in the previous game is not quite the right thing if you want to kill off the quarians and keep the geth, since this decisions weakens the Geth War Assets, but it is the right thing if you want to either kill off the geth and keep the quarians, since destroying the heretics gets you stronger quarian War Assets, or broker peace between the geth and the quarians, since making peace is easier if the heretics are destroyed than if they're rewritten.
In one mission, you're forced to choose between saving the Rachni Queen/Rachni Breeder, or saving the an elite squad of krogan called the Aralakh Company. Which choice is this trope, and which choice is the right thing, depends on whether you saved the Rachni Queen in the first game, in which case choosing the Aralakh Company over her in Mass Effect 3 is not quite the right thing since the Aralakh Company gets you less War Assets; or whether you killed the Rachni Queen in the first game, in which case you need to save Aralakh Company instead since it's saving the Rachni Breeder surrogate that's not quite the right thing, since the Breeder will eventually turn on you and kill off a a lot of the Alliance Engineering Corps.
Not That Kind of Doctor: During the "From Ashes" mission, your other squadmate will ask Liara if she has ever dug up any dinosaur bones during her time as an Adventurer Archaeologist. Liara replies with a mini-lecture on the difference between archeology and paleontology before she realizes they're kidding. James Vega sheepishly quips, "I just like dinosaurs..."
Garrus asks the same thing, he as well knows full well what Liara's doctorate is in and the whole conversation becomes a Mythology Gag about Liara's wide-eyed naive alien-girl role in Mass Effect 1.
Liara: Oh. You were joking, weren't you? Garrus: A little, but, at least you're catching on these days.
Or with EDI:
Liara: Oh. That was a joke, wasn't it? EDI: No. A joke has a specific structure. This was "messing with you".
Not So Different: Shepard can compare Grissom Academy to the Cerberus facility on Pragia. Jack does not like the comparison.
Not What It Looks Like: The final confrontation in the Citadel coup. Shepard bursts through a door during the middle of a terrorist attack orchestrated by a group Shepard acknowledges having worked with with his/her gun raised on one of the leaders of the galaxy. It's actually because Udina worked with Cerberus to orchestrate the attack, though the Virmire Survivor has no way of knowing that. Unless Shepard and the Virmire Survivor have repaired their relationship to the point that s/he can convince them of what's really going on, Shepard or one of his/her squadmates will have to shoot the VS.
Oblivious Guilt Slinging: Everything Eve and Wrex say during and after the Priority: Tuchanka mission if you decide to sabotage the genophage.
Oblivious to Love: If they are both assigned to the geth dreadnought mission, Garrus and Tali can discuss the turian chocolates that Dr. Michel gave to Garrus. Tali reads into it, but Garrus does not seem to realize that Dr. Michel might have been trying to send a signal.
Odd Friendship: Tali and Legion actually refer to each other fondly, Tali in particular talks about her whole perspective being shifted because they kept in contact with each other between ME 2 and ME 3 (until Legion's disappearance).
Off Model: When you start conversation that doesn't enter cutscene mode, the NPC's head turns to look at you. Apparently, the limits of movement aren't coded effectively, since character's heads often go past 90 degrees and into the Exorcist territory.
The Defense Committee has an excellent one as they see the first Reaper descend from the clouds. Made even better by the fact that they have finally realized that Shepard was right.
The Cerberus Mooks on Mars have one when they finally realize that Shepard is with the Alliance reinforcements.
Wrex has a lesser one on Sur'Kesh; after losing his temper and attacking some salarian guards, he finds the laser sights of two salarian snipers on his face. Shepard intervenes before things get messy.
Garrus says those exact words on Sur'Kesh when an elevator's doors open to reveal a bomb.
In Leviathan, everyone's reaction to discovering the mining team on Mahavid have never heard of the Reapers.
Shepard: What year do you think this is?
In a hilarious twist, Shepard has one when EDI jokes about the Normandy's oxygen-venting systems failing if she discovers something interesting.
Old Save Bonus: Taken Up to Eleven. The game tracks over a thousand variables from a save file that went through the previous two games, including:
Major plot threads like who leads the krogan, whether the Citadel is led by the original council or the replacements, who you chose to pursue a relationship with, Whether the geth and the quarians can find peace or not with each other, etc...
How many of your Mass Effect 2 squadmates survived, and whether they were loyal. It can make certain character-centric missions in 3 much easier.
An imported Shepard (and, by association, his/her squadmates) all start at the level you ended Mass Effect 2 with. A Level 30 character imported in gets all his points to spend right off the bat (although most of it gets assigned to the powers it was assigned to).
The game tracks whether or not you completed the previous game's downloadable content. If you completed "Bring Down The Sky" from Mass Effect 1, and saved the hostages, Balak can show up again; he also shows up if you didn't save the hostages and then left him for dead. If you completed "Lair of the Shadow Broker", you can get bonus intel. Completing "Arrival" nets extra dialogue during a couple of conversations and prevents a reduction to a war asset (who had to do Arrival since you did not).
If you managed to save Kelly Chambers and followed a specific set of circumstances, you can get a bonus War Asset and bonus intel from a tropical fish bought in the previous game.
Importing a completed save of the iOS game Mass Effect: Infiltrator into a new ME3 save file nets an exclusive War Asset.
Taken to the point of self-parody in the Conrad Verner sidequest, which can bring up three seemingly-meaningless quests from the first game - Gavin Hossle, the ancient asari writings and the Elkoss Combine license - in rapid succession. Conrad is amazed. Oh, and the ending changes based on a fourth flag.
The upgrades you bought for the Normandy (Thanix Cannon, Heavy Ship Armor, Multicore Shielding) transfer as additive modifiers to the SSV Normandy war asset.
One-Hit KO: Phantoms (if they haven't been disarmed), Atlases, Brutes and Banshees can all do this to players who get too close. Fortunately, all except Banshees will only insta-kill after they've already connected with a melee attack, and the game auto-saves before each Banshee fight. Banshees will only Grab you if they're glowing (which they are most of the time).
Optional Stealth: In the beginning of Citadel you get a silenced pistol which can be used to kill enemies without alerting the rest.
Our Founder: There is a large statue of Jon Grissom in Grissom Academy.
Outrun The Blast Wave: At the end of the game, the Normandy is seen attempting to outrun the blast wave caused by the overload of the Mass Relays. It fails and is forced to make a crash landing on an unidentified planet.
Overshadowed by Awesome: Jason Prangley. If Jack survived Mass Effect 2, Prangley is just another one of Jack's students. If Jack didn't survive, Prangley is the students' teacher. And to his credit, he is a good leader; it's just that his teaching style is different from Jack's (Jack is the "psychotic biotic"; Prangley is a more traditional "you can do it!" kind of teacher). Unfortunately being a "good" leader does not always mean being a "great" leader: while he successfully saves Rodriguez's life just like Jack does, unlike Jack the enemy does manage to kill Prangley with one final shot.
If they both survive to the end of the game and were not romanced by Shepard, the player can walk in on Garrus and Tali hooking up.
If they return to the Normandy and Shepard encourages them to enjoy life while they can, Ken and Gabby can be found making out in the sub-deck. Both try to cover what they were doing and are aghast that they were caught.
Ashley and James can hook up in Citadel if the former was not romanced.
If neither are romanced, Shepard can suggest this to Jack and Miranda in Citadel. No word on whether they actually do anything about it, though theirreactions suggest they didn't.
Shepard: I fight for freedom, mine and everybody's. I fight for the right to choose our own fate. And if I die, I'll die knowing that I did everything I could to stop you. And I'll die free. Starchild: So be it.
People Puppets: After getting Reaper implants, the Illusive Man gains this power. He uses it to keep Shepard and Anderson still during his final monologue, then forces Shepard to shoot his/her mentor.
Pin-Pulling Teeth: A turian is seen biting off the pin of a grenade in the ending battle of the game.
Pintsized Powerhouse: The Alliance Infiltration Unit in multiplayer. This robot is about as small and wiry as EDI, yet her punches cryo-uppercuts send enemies flyng just like krogan do.
Pistol-Whipping: One of the available melee attacks. It is faster than using the Omni-Blade, but for obvious reasons, does less damage. The melee damage can be upgraded with the combat tazer attachment.
Shepard and his/her squad have every reason to believe that they're going to die during the final push against the Reapers, but that doesn't stop Shepard and a romanced Garrus from calmly discussing whether they should settle down and start a family after the war is over.
Shepard and a romanced Liara once again bring up the thought of little blue children after the war.
Earlier, Shepard promises a romanced Samantha that she'll buy her drinks in Vancouver after the Reapers are defeated. Sam is less than impressed, and laments that Shepard never takes her anywhere nice.
All of the squadmates will discuss plans for the future after the war. Javik, for example, can end up deciding to write a book with "Dr. T'Soni", live like a king on Kahje, or join his comrades in death.
Plasma Cannon: Any geth weapon other than the basic Pulse Rifle and Javelin will be one. Though they do not actually fire projectiles in a plasma state, they launch conductive torus-shaped projectiles which are highly charged before firing and designed to shatter on impact. The shattering causes the charge to arc between the fragments and the whole thing gets excited to a plasma state. The penetration is low, but the stopping power is fantastic.
This may happen with Kaidan and a Female Shepard - though he desperately wants it to be more.
Please Wake Up: In the Geth Consensus level, the geth memory from the Morning War where the martial law enforcers corner and blow up a geth and his sympathetic owner...
Damaged Nameless Geth: Creator Megara, what is your status? (Beat) Damaged Nameless Geth: ...Creator Megara?
Point of No Return: There are two points in the game where, once you complete that part, previous parts of the game become inaccessible.
Tough: Once you complete Priority: Tuchanka, many Citadel sidequests can no longer be completed, as the next time you visit the Citadel it is attacked by Cerberus and the people to whom you report your success can no longer be accessed. Completing the Citadel mission in turn makes any as-yet-uncompleted missions on Tuchanka and the Grissom Academy mission also unavailable.
Merciful: Once you make the assault on Cereberus HQ, the endgame begins. When you first try to move in, Hackett explicitly points this out, saying that the Reapers will take notice and the assault on Earth will have to begin.
Political Correctness Gone Mad: Joker tells a 1000 year old joke about a krogan and salarian. EDI charges that it's stereotypical, and such stereotypes of krogan being nasty, war-minded brutes led to the development of the genophage. Joker counters that it's one of the only jokes you'll hear both species tell, and that comedy is a way for people to air out nasty thoughts and grievances.
Porn Stash: Joker apparently has seven zettabytesnote For the non-computer geeks out there, that's roughly enough data to fill fourteen Internets of explicit material stored somewhere in the Normandy's computers. According to a Cerberus information terminal you find in their HQ, this collection was weaponized by EDI and used to spam Cerberus electronic warfare division computers trying to gain control over the Normandy. Of course she was joking about it being all Joker's.
Of the holographic variety, used by batarian characters to punch enemies across the room. The batarian "enforcement gauntlet" functions by flash-forging several blades around the wrist as the user winds up a punch. Once the punch is landed, a kinetic barrier is generated along their length and rapidly expands. The result of taking one of these to the chin causes understandably excessive cranial trauma. The batarian Gauntlet lets any character do this. Including the volus.
N7 Demolisher Engineers infuse their omni-fists with microgrenades, connecting their punches with a solid bang!
Alliance Infiltration Units gain a cryo-infused uppercut as a heavy melee, which will send enemies up into the air.
Gamestop pre-orders include "Defender Armor" and an N7 Valkyrie Assault Rifle (the only weapon not covered by the Collector's Edition weapon pack).
EA's Origin network offers the AT12 Raider Shotgun.
Others get the Argus assault rifle, which is also a midrange weapon.
Press X to Not Die: If you cannot talk the Illusive Man down in the finale, failure to hit the correct prompt results in this after he kills Anderson. And yes, he kills you too if you do not take the second prompt. Hope you like going through the dialogue again!
In a less literal fashion, there are a couple of situations where Shepard has to kill an enemy (or three, in one case) quickly or she/he'll be killed instead.
Previews Pulse: 3's trailers had them. The "pulse" is actually in-universe: it's the sound the Reapers generate when charging their massive lasers.
Previously On: If you did not play either of the previous two games, there will be two video prologues explaining the story so far and the races of the galaxy.
Pro-Human Transhuman: If you choose the Control ending in the Extended Cut, Reaper!Shep becomes this, especially if they were a Paragon.
Punched Across the Room: Adepts and Vanguards have biotic heavy melee attacks; the former gets an open-palm strike that focuses on distance, the latter gets a super-punch (that can be used right after Charge). Batarian characters can also do this to enemies with their enforcement gauntlets, which generate a giant holographic fist for a huge punch. The N7 Demolisher has a more literal example, as her omni-tool uses a concussive blast that trades off damage for additional Knockback. Finally, the Alliance Infiltration Unit deceptively small frame can uppercut enemies across the room.
Punch Packing Pistol: While not quite as powerful as in the first game, pistols have received a huge buff since the second. Most pistols outclass their low to mid level long gun counterparts. However, pistols ultimately Can't Catch Up with the introduction of the Infinity+1 Sword versions of assault rifles, shotguns, and sniper rifles.
The Predator and especially the Eagle have better accuracy, higher damage, and lower weight than the Phaeston and Avenger assault rifles.
The Phalanx not only has the above advantages over its assault rifle counterpart, the Vindicator, but the fact that it's semi-automatic instead of burst fire means it's easier for it to land headshots.
The Carnifex makes the Viper and Mantis completely obsolete; just as accurate, weighs less, holds more ammo, and can kill most enemies in one or two headshots.
The Paladin is an upgraded Carnifex which makes all sniper rifles barring the Widow, Black Widow, and Javelin completely pointless.
The Talon is a revolver that shoots shotgun rounds. Its range and damage are far superior to the Eviscerator, Katana, and Scimitar shotguns. And, like all other pistols, it weighs less.
The Suppressor heavy pistol boasts a high rate of fire and the highest headshot multiplier in the game.
Punny Name: The default stage at the Armax Arena in the Citadel DLC is called Wingman. The setting? On the wing of a turian cruiser.
Purely Aesthetic Gender: Played straight in multiplayer with the basic human characters of all classes, as they have completely identical stats and abilities. Averted with everyone else, whether they are human or alien, since either a given race/class combination is exclusive to one gender, or, as with the quarian characters, the male characters have completely different abilities from the female ones.
Put on a Bus: Early in the game, the Virmire Survivor is critically injured and has to spend most of the first act recovering on the Citadel. Later, the player is given the option of bringing them back into the party or keeping him/her on the bus, in which case, they go join Admiral Hackett and become a war asset. Of course, this assumes that they are still alive by that point...
Put the "Laughter" in "Slaughter": Krogan multi-player characters, when they enter close combat. Also, Grunt has a disturbing tendency to sort of giggle as he kills things.
Krogan PC: Hah! They're dead!
Putting the Band Back Together: Of the five surviving members of Shepard's ME1 six squadmates, four of them — the Virmire Survivor, Garrus, Tali, and Liara can rejoin the Normandy if they survived the previous games. Non-squadmate characters, including Engineer Adams, Doctor Chakwas, and Ken & Gabby can be recruited to take their old posts on the Normandy.
The entire point of the Citadel DLC, one last time. Wrex also becomes a temporary squadmate for the DLC storyline and Armax Arsenal Arena.
Pyrrhic Victory: Low War Asset tallies before the final battle result in greater and greater damage to your forces, which impacts what state galactic civilization exists at after the conflict. If you have very low War Assets, you don't even get to choose your ending; you either get Destroy or Control based on your choice for the Collector Base.
Casey Hudson: If you just rip straight down the critical path and try and finish the game as soon as you can, and do very little optional or side stuff, then you can finish the game. You can have some kind of ending and victory, but it’ll be a lot more brutal and minimal relative to if you do a lot of stuff.
The Quisling: Udina decides to team up with Cerberus, and is responsible for the Cerberus raid on the Citadel, and can kill off most of the Council if you don't stop him.
Rage Quit: Multiplayer has experience and money earned for kills, completing objectives, and surviving waves. The player forfeits this if they quit before the mission ends in either success or failure, discouraging this trope. Unfortunately, this also causes players to forfeit any rewards whenever the game crashes or disconnects during a match.
Ramming Always Works: Subverted in the Omega DLC. Cerberus manages to shoot down Aria's ship when she tries to ram it to breach Omega's defenses.
Real Song Theme Tune: Similar to the N7 hoodie, the Citadel DLC retcons the game's main love theme ("I Was Lost Without You") into being from in-universe movie Fleet and Flotilla as the love theme for its turian and quarian protagonists. If Tali is Shepard's love interest, she sings along to the theme. Similarly, "Vigil's Theme" becomes a song which Liara heard and learned to play on the piano.
Kelly Chambers is not a badass soldier like Jacob, or a biotic genetically engineered goddess like Miranda. She is a Yeoman with a degree in psychology. When Cerberus come for her, if Shepard had not convinced her to change her identity, she will die. There is no fight. There is no battle. Shepard is not there to help. She is asked if she is Kelly Chambers, and when she says yes, she is shot between the eyes at point blank range.
After seeing him/her shooting down 160 meter tall Destroyers with heavy weapons, powerful backup and tactics, the game has Commander Shepardtake on Harbinger the largest and most powerful Reaper with a small company of ground forces with little forewarning. It goes about as well as you'd expect.
In the Extended Cut DLC, the Refusal ending, where Shepard refuses to use the Crucible and tells the Catalyst that s/he, and the rest of the galaxy, will die on their own terms, not its. All of Sword, Shield, and Hammer are massacred and the galaxy falls to the Reapers.
The game pretty much lampshades how much stress and trauma The Hero would have when he or she has to keep saving the day all the time. Shepard is constantly bordering on the Despair Event Horizon and expresses multiple times that s/he's barely holding it together. There are hints that s/he's nearing a complete nervous breakdown and the presence of his/her friends to comfort and bolster him/her is all that keeps him/her running at times.
Reality Is Unrealistic: Cortez mentions Alliance combat space-craft using "Auditory Emulators" in battle to count for the lack of noise in space.
Reassigned to Antarctica: Listening post X-19 is described as this as it monitors the rachni homeworld and no sentient life has been spotted in the star cluster for over a thousand years.
Shepard has a chance to end the war between the quarians and the geth (relatively) peacefully, though there are many conditions that have to be met for this to succeed.
The krogan/salarian/turian enmity can be mended to the point where the three races start cooperating — something deemed impossible for at least several centuries.
You can also recruit the surviving batarians for your cause, ending their hostility towards the humans. Especially powerful if Shepard's background (specifically Colonist and/or Ruthless) involved batarian raiders.
Regenerating Shield, Static Health: With a twist: The health bar is split into five segments. Each segment will regenerate, but any depleted segments can only be replenished with Medi-Gel. The new health system encourages players to be more careful in combat, as well as extra Experience Points being given for picking up Medi-Gel past your carrying capacity.
Subverted with Vorcha Multiplayer characters, whose special ability is regenerating health with their Bloodlust. The more kills they get in a short window, they move faster, kill quicker, and regenerate health more. It's balanced out by their rather pathetic shield strength, however.
Same with the Krogan Warlord, except it's a passive ability, his barriers aren't weak at all... but he can't take cover.
Redemption Equals Death: Mordin sacrifices himself to cure the genophage. Legion also does this if you are able to stop the geth/quarian war, as uploading the Reaper code to the geth requires his personality to be uploaded as well, essentially killing him in the process. In his case, the redemption of the entire geth race equals his death.
Relationship Values: Hidden, but present, most noticeably for Ashley and Kaidan: at the Mexican Standoff at the Citadel, a perfect relationship with them results in them automatically trusting Shepard, while worse relationships require higher and higher persuade checks until finally the player has no choice but to kill them.
The relationship values, in addition to affecting dialogue, determines which squadmate(s) step out of the Normandy after it crash-lands in the ending.
Revolvers Are Just Better: The M-358 Talon is a revolver handgun favored by Cerberus Guardians. It is basically a hand-held shotgun although the cylinder holds only 4 shots rather than 6. Unfortunately it is missable and will not be able for purchase if not found during the Priority: The Citadel II mission.
Required Party Member: Liara is required for Thessia and Eden Prime (assuming you downloaded "From Ashes"), Tali is required for the first and last Rannoch missions, and EDI is required for the assault on Cerberus HQ. In addition, party members are chosen for you for the missions on Mars (James and the Virmire Survivor, with Liara replacing James a short time into the mission) and Palaven (James and Liara, with Garrus replacing the latter if he survived ME2).
Aria doesn't trust anyone on the Normandy but Shepard, so the Omega DLC forces you to use only Aria and Nyreen.
Citadel requires Guest Star Party Member Brooks for the second mission, although there is no combat involved. The beginning of the DLC storyline also chooses specific squadmates to join up with Shepard during the first mission (your love interest/Liara, Wrex/James).
One of the Armax Arsenal Arena's challenges requires you to use a squad of only Alliance marines (Shepard, James, and Kaidan/Ashley (if they are in your squad)).
Retcon: In the Extended Cut DLC, the mass relays are shown merely suffering damage instead of blowing up, and the Normandy suffers a lot less damage upon crashing.
The asari were given an advantage over the other races because the Protheans picked them to be uplifted, with the idea the asari would use the Prothean tech to advance other races. Unfortunately, the asari decided to keep all of the Prothean tech to themselves, despite the mandate that all Citadel races donate Prothean artifacts and tech to the Council, such as when the Alliance had to do that when a beacon was discovered on Eden Prime in Mass Effect 1. As a result, the galaxy races were more unprepared for the Reapers.
The Leviathan of Dis, the corpse of a genetically engineered organic starship which was mentioned in Mass Effect 1 and by Balak, is revealed in this game to have been the corpse of a Reaper. This was one of the key reasons for the complete destruction of the Batarian Hegemony, as its corpse had indoctrinated many members of the batarian military and government who sabotaged their home systems defenses. The Leviathan DLC goes on to reveal that the real Leviathan—the thing that killed the Reaper—is one of the last surviving members of the species from which the first Reaper was created.
The final scene of the game reveals that the Citadel is home to an AI, referred to as "the Catalyst," that created and controls the Reapers. It uses them to harvest advanced organic life and preserve it in Reaper form out of a belief that a synthetic rebellion is inevitable, and that if it did not interfere then eventually the synthetics would wipe out all life, whereas with the Reapers at least the primitive races can continue to exist.
Revenge Before Reason: Oh, Lord, the quarians under Admiral Gerrel. Summed up perfectly if the geth destroy the quarians because they wouldn't listen to Shepard to stop attacking.
Cerberus, for several reasons, as per the Illusive Man's orders. The Illusive Man's belief is that the Reapers don't want to destroy all sentient life — because if they did, there'd be no reason to have left humanity alone last time or to go through this trouble to "harvest" races. He believes that since the Reapers see something valuable in humanity, it would be wiser to gain control of the Reapers and guide their plans with humanity's interests. Okay — all of that is absolutely true, but it doesn't change the fact that the Reapers plan to wipe out all galactic civilization as it exists and that humanity would effectively cease to exist being essentially "human", which would make preserving the species moot. Furthermore, the Illusive Man is indoctrinated, and it's made clear that the indoctrination would have prevented him from actually gaining control at all and was probably making him more sympathetic to the Reapers' goals than humanity's. Despite all of that, however, Shepard can choose to go through with TIM's plan and s/he can take Control of the Reapers in his stead.
On the Citadel, you can hear Rupe Elkoss (the billionaire owner of Elkoss Combine) lambaste the Sanctuary colony on Horizon, advising his conversational partner not to run to that "scam of a place" since he assumes that they are making money off people's desperation. He is right that it is a bad idea to go there, but instead because Sanctuary is a secret Cerberus atrocity factory focused on figuring out Indoctrination, using refugees as unwilling test subjects and having a secondary function of producing a lot of Cerberus mooks from some of the hapless refugees.
Robot Dog: The Collector's edition will give Shepard one - it is basically a FENRIS mech with blue 'eyes' instead of red.
Robot Girl: EDI becomes this after the team captures a robotic Cerberus infiltration unit.
If you punched her in one of the previous games, she'll hilariously try to subvert this trope by dodging your first punch and attempting to counter-attack with one of her own, thereby prompting you with a second renegade interrupt!
A minor event on the Citadel has Shepard seeing a disgruntled customer trying to get a refund from a shop. He has been trying since Mass Effect 1! In a Pet the Dog moment, you can support him, finally getting him... his fifteen credit refund... for a toaster oven.
In the Blasto radio drama, Bubin the Elcor C-SEC officer prefaces everything he says with "Badassfully:". His sister prefaces everything with "Coquettishly:".
Everyone makes a reference to Garrus Vakarian's constant tweaking of the weapons systems on the Normandy, including suggesting that he get back to the guns when he first joins your crew in the third game so that he can do more calibrations. He then, of course, does so, for the third game in a row, though at least this time his "go away" dialogue isn't that he's running calibrations... even though he is. There is a conversation between Legion and Garrus wherein Legion, an AI, claims the guns cannot be made more than 0.32% more efficient, and Garrus then promptly improves them by 0.43%. He's just that good.
Garrus then tells Legion his cunning master strategy which basically amounts to a Montgomery Scott tactic. "You just have to hold back a bit more than expected."
Conrad Verner makes yet another appearance, causing yet more trouble by trying to emulate Commander Shepard, this time joining Cerberus and accidentally helping them sabotage medigel dispensers. His total ineptness is somewhat subverted, however, as when he yet again offers to help you, Shepard, in exasperation, tells him that s/he's working on a (top secret, not supposed to be talked about at all) Prothean dark energy device to save the galaxy. As it turns out, Conrad Verner studied dark energy and xenotechnology at university, and actually contributes some data to the Crucible project. To be fair, Verner is a bit crazy, so Shepard probably assumed no one would believe him anyway if he blabbed.