Artificial Brilliance: Dark Matter. They essentially are on par with Ark Hunters, with their own Energy Shields, tougher than most armor, and even squad-like tactics. If a Nano-Effect lights them on fire, they dodge roll until the fire is snuffed out. If a sniper tries to shoot the front of the head instead of the back, they will immediately run and duck for cover. They will even throw grenade to flush out an enemy from their cover spot.
Auto-Revive: You have a self-revive that recharges over time.
Arkfall Breaking Bug: A current problem that can come up is that sometimes, during major Arkfalls, one of the smaller ones won't complete despite the objective being completed, therefore making the Arkfall unable to be completed, making everyone's efforts useless.
Big Damn Heroes: The Arkfall system turns players into this. During major Arkfalls the first stage is four or more smaller events, it's quite common for a single or pair of players to be trying to hold the line at one and be reinforced by two dozen players riding in on ATVs, dune buggys, and Dodge Challengers.
Can also be a subversion as well: One player who knows what they're doing is easily capable of beating a minor Arkfall challenge. The two dozen cavalry who ride in to the rescue then subsequently turn all the enemies into outright bullet sponges with orders of magnitude more health than they used to have.
Body Horror: The result of getting hit and killed by an Infector.
Broken Bridge: At what's left of the Golden Gate Bridge, there is a very large mech. Getting too close gets you blown to hell. Eventually you get access to an ICBM that blows it to bits, letting you advance into what's left of San Francisco.
Removed in the free-to-play version. Apparently, beta testers didn't like it when a major arkfall was on the other side.
Bug War: Anytime a large Arkfall occurs with the primary enemies being hellbugs. Expect battle zones to be filled with car sized bugs duking it out with literally dozens of ark hunters.
And they can show up in the bonus waves of other factions' Arkfalls. Good News: they also attack the enemy faction. Bad News: when both factions fight you, they synergize VERY well (sticky tar throwers + rocket launchers = trip to the hospital).
Christmas Rushed: When first announced, the developers of the game made a lot of pie-in-the-sky promises that unfortunately they were not able to implement because they were under a deadline to launch the game at the same exact moment the show began broadcasting. The developers have been open about this happening, and are trying to add the promised features and content to the game as quickly as they can through updates and downloadable content.
Crapsack World: In comparison to the show, which has more of a hopeful wild-west vibe, the game's setting (the San Francisco Bay area) has an incredibly hostile environment that one could be forgiven for thinking takes place in a more destructive After the End type scenario.
Car Fu: You can kill most low level enemies by running them over. It even levels up your driving skill with that vehicle type!
Charged Attack: Some weapons can be charged up to make their next shot deal more hurt (better chance of elemental debuff, multiple bullets in one release, etc.)
Cybernetics Eat Your Soul: 99ers, a group of miners, turned psychotic after getting cybernetic implants - replacing more and more of themselves until they were over eighty percent machinery. It's implied the original psychosis came from an external third party, however.
Cycle of Hurting: Grenade launcher using enemies can do this to you if you're not careful and stand still when fighting them.
Enemies can knock you back or knock you off your feet. Repeatedly.
Death or Glory Attack: Hellbug Monarchs expose their vulnerable underside when rearing up to attack. But if you don't stun or kill them...
Enemy Civil War: Each of the enemy factions in Defiance represents a different extreme, so you're bound to occasionally catch a break when the bugs and raiders kill each other instead of you. Hellbugs are animalistic and hated by everybody (it doesn't help that they're the game's Goddamned Bats), mutants are human supremacists who have been driven insane by the Votan's terraformers; raiders are multiracial bandits who like to kill everyone for scrip, Dark Matter is Defiance's version of The Thalmor and make deals with the other factions only to backstab them constantly, the 99ers are cyborg miners who have gone insane, the Volge are blood knights who want to conquer everyone, the afflicted are The Infected, the Scrappers are The Terminators (on low budget!), and the Grid are the Borg. You've got every type of basic enemy and they all hate each other almost as much as they hate YOU. Meanwhile, your boss is trying to terraform the planet back to the way it was, save the Earth, and commit mass genocide to stop the Crapsack World you constantly fight in. That makes you the villain protagonist who saves the weak and kills everyone else, so it's no surprise that enemies will prioritize ark hunters, yet still have to fight each other due to irreconcilable differences.
Gameplay and Story Segregation: The shields in the game can take a LOT of damage, and even heal your character while at full. In the TV series, if there are any shields, they don't do much good for Defiance or its enemies; Volge die instantly from a few regular headshots, when in the game the Volge shield is one of the most stable and enduring. Also, Armored Hellbugs in the TV series are REALLY easy to kill (Nathan's pistol kills a smatterling with all the bullets in the clip).
Gravity Barrier: The hills around San Francisco are set up in a way that guides you through the main storyline. A decent vehicle will help you get past them later, if you're interested in scaling them.
Half-Human Hybrid: While this trope is implied to happen in the show, the game outright confirms it with the introduction of William Parraba; the first person conceived between a human and a Votan (an Irathient, to be precise).
Healing Shiv: The Bio-Magnetic Gun, or BMG. It can either drain energy from enemies or heal the user and their allies.
Insufferable Genius / It's All About Me: Von Bach all the way. From his introductory scene he paints himself as an arrogant know-it-all, and imposes himself as future savior of Earth due to him having a Ark core. He also repeatedly hits on various female NPCs like Cass Dukar and Ara Shondu, in a manner that suggests they owe him for having the Ark core and being the possible savior of Earth.
Interface Screw: Electric-element attacks disable your friendly nanomachine AI. This doesn't kill her, but it prevents you from using the HUD while it's active, including weapon zooming for some reason.
Invisible Wall: The dark areas on the map edged with a yellow line are this. Sometimes they don't quite match up.
It's Up to You: Justified when you fight Nim Shondu; his EGO augmentation makes him superhuman (he combo-killed 18 men at the Battle of Defiance with a SWORD.) and you are the only one with an EGO while everyone else has to hold off Dark Matter.
Les Yay: In a blink-and-you'll-miss-it moment (during the Human-Irathian hybrid quest), you'll see Rosa and Eren hold hands.
Mirror Boss: Nim Shondu has the same four action skills that the ark hunter can use, only better. During the first round, he'll use blur and cloak in tandem to get close to you and perform well-timed charge attacks. During the second round, he'll cloak and deploy multiple decoys that can deal actual damage; his limit breaker is to surround you with decoys across the room and have all of them charge a ranged attack at the same time. During the final round, he'll lose it and go into permanent overcharge, which looks like a cyberdemon; he spams ranged attacks. To make things fair, he uses a force blade and his ranged attacks are non-bullet.
Monumental Damage: The broken Golden Gate Bridge is shown in loading screens, and eventually, seen in person. Also, there's the fact that San Franciso is now a square island, which means that the Bay Bridge, San Mateo Bridge, Dumbarton Bridge, SFO, etc. are all simply gone.
Silicon Valley somehow survived... the land, that is. Almost every building and road is in RUINS, made more emphasizing by the lack of ecological damage.
Mood Dissonance: Due to the basic use of stock audio for every sidequest, you could do a mission that has a jarring and disturbing end, yet the quest giver will remain positive and cheerful. Example: Rosa's girlfriend went on a 45-day spirit quest only to get burned and hanged by bandits. Rosa's response?
Rosa: Oh yeah! This is the news I wanted to hear!
More Dakka: As you progress in the game, your simpler weapons have some crazy counterparts, like a grenade launcher that shoots grenades that blow up into six more grenades, Sub Machine Guns that can unload a fifty round clip in under three seconds, and double-tapping sniper rifles.
Random Number God: The above-mentioned Random Events make the RNG very unforgiving during racing. Since the races take place on open terrain, the random events can interfere, potentially screwing up a Gold Medal time by dropping a Hellbug in your path.
Events will also appear in areas where an open-world PVP Shadow War is occurring, even right on top of one of the control points being fought over.
The Reveal: <PLEASE MAKE THIS A NOTE> During the Battle of Defiance, the enemy was on the verge of curb stomping the few remaining soldiers bunkering at the fort, so Nolan, Jon, and a few others made the most significant decision of the series: they used a WMD, the Ark Core, which is a copy of the McGuffin Set that you've been chasing the whole game. Which would have been fine, aside from the unholy suffering of the thousands of soldiers and few civilians who were utterly blown away (one of them survived, and he was NOT HAPPY), if not for the fact that THE ARK CORE IS THE CENTRAL PROCESSING UNIT OF THE ARKS. Cue arkfalls. They were trying to stop a racist army from slaughtering millions of innocents out of spite, and ended up causing the apocalypse instead. Jon and company have kept this secret until they realized that Nim didn't have to be a rocket scientist to activate a second Ark Core and murder everyone.
Short Range Shotgun: Played straight and averted depending on the type of shotgun. Some are slug based and give up straight damage for a considerable range increase, whereas others are effectively useless beyond five feet but kill almost anything dead in one salvo. Still others are essentially misnamed grenade launchers.
Shout-Out: If a weapon looks like it's inspired by District 9, it probably is; according to one of the concept artists, the art director was a huge fan of it.
Stat Grinding: Using weapons/vehicles increases your stats for using weapons/vehicles of those type. This transfers over to the mini-challenges, which is REALLY useful for winning an insanely unforgiving time trial.
Unflinching Walk: Subverted and lampshaded. You, Jon Cooper and Torc Mok walk away from a major demolition mission. Torc turns around to look, Jon says that you don't do that only for Torc to ask what's the point of big explosions if you don't enjoy them.
Zombie Apocalypse: The plague from the show supposedly causes this in the game. Jarring in that no such zombies or "afflicted" were in the show.