These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
The grineer are based out of earth and the lore implies that they are the result of humanity attempting to preserve itself via extensive cloning. The corpus are men in suits accompanied by robots. Tenno operatives routinely go to their planets and exterminate them by the hundreds, sabotage their economies by destroying their (non-military) mining installations, and destroy their ships. And one of the grineer bosses is marked for assassination simply for attempting to reverse the genetic deterioration of his people. Is it a stretch that the Tenno might actually be the villains here?
The Lotus: Savior of the Tenno and leader of the resistance against the Grineer military dictatorship, or Chess Master playing an army of amnesiacs to steal Orokin technology and eliminate threats to her plans (military or otherwise)?
Corpus transmissions have referred to her as "traitorous", and even the developers have hinted that she's not to be trusted.
So it turns out that the reason why the Stalker is murdering Tenno is because the Tenno murdered the Orokin. Why exactly, we still don't know yet.
Base Breaker: Prime weapons are starting to become one of these. On the one hand they're powerful item rewards for completing missions in the Void and they're aesthetically very pleasing with gilded edges and flowing lines like the rest of the Orokin technology. They make an excellent reward for the later game play. On the other hand, they're typically direct upgrades to default weapons with significantly better stats in a number of important fields like damage and fire rate. This wouldn't be so much a problem in and of itself but a lot of people have invested rare resources in upgrading these default weapons or even bought them with real money before the Prime version came out. This has lead some players developing "prime paranoia" and avoiding the use of catalysts, formas, or heaven forbid platinum on something that's just going to be made obsolete later.
The Soma assault rifle is this now, too. It's an assault rifle/light machine gun hybrid with low damage... but exceptional critical stats. A properly built one will beat most weapons in the game in terms of DPS. It's also available to low-ranked players and doesn't even need dojo research. It's since been recently changed to be available to high-ranked players, but players who already had the Soma get to keep and and continue using it.
The Nova Warframe, see Game Breaker below. There are some player which consider her to be fine and advocate that the other Warframes should be buffed to her level, while other say that she should be brought down a bit more together with the former.
The Gravidus Dilemma event.
Bribing Your Way to Victory: Many weapons and Warframes can be bought in completed form for Platinum with a coveted Orokin Reactor or Catalyst pre-installed whereas players would otherwise have to craft all these items over intervals of real time after farming the required materials. The materials themselves can also be bought and the build times circumvented using Platinum and the cash shop also contains mod packs with guaranteed rare mods. All players have access to all items that actually affect gameplay (barring only Warframe and Weapon slots) with only cosmetics being cash shop exclusive but DE certainly sells a high level of convenience.
Character Tiers: Somewhat invoked - certain frames are meant to be flat-out better than others in certain ways, others are not. With frequent balance changes to abilities, weapons, and frames, the tiers themselves can fluctuate regularly. Plus some of them are situational. For instance;
Ember's fire-based powers make her amazing against the Infested - but less so against the Grineer.
Volt's electricity-based powers? Very effective against Corpus, okay-ish against Grineer, much less effective against Infested.
Ash... well, highest max health without considering modifications(Tied with Saryn now), good armour and damage mitigation (increasing effective health), good shields, high sprint/run speed, and a nice set of powerful and effective abilities. He's not much of a team player, though.
Infested Ancient Disruptors. ONE hit will screw up your interface, sap your shields to zero and, worst of all, drain your entire energy store. Since energy doesn't regenerate on its own unless you have the right artifact (in which case it regenerates painfully slowly) one hit from a Disruptor when you're being attacked by a swarm of lesser infested will basically kill you in one go, especially since they knock you down.
Toxic Ancients are surrounded by a poisonous cloud that bypasses shields and they leave behind said cloud when they die. An inattentive player on anything other than Rhino (whose Iron Skin temporarily negates the poison and blocks the Ancients' knockdown attack) can die in seconds upon running into several of these noxious beasties, especially on higher levels when they spawn in packs and their poison damage is ridiculously up-scaled. Such situations are the bane of otherwise top tier casters like Nova and Nyx because their amazing powers will not save them as they melt in the toxic green miasma. It also does a number on defense objectives.
The Fusion Moa is a bit more threatening than most Corpus units because of its highly damaging beam attack, but the real danger is that if not killed fast enough it can release a flying Drone with even heavier armor than its parent unit and the greatest firepower of all Corpus proxies, capable of stripping any Warframe naked in seconds at higher levels.
Grineer Napalms have a nasty AoE on their weapons - big enough that it can hit you through a non-Stretched Snow Globe - and the damage-over-time can mess you up very fast. To make matters worse they don't use a Painfully Slow Projectile like their Bombard comrades.
In recent updates the Grineer Scorchers have joined the ranks of this enemy type. Their flames can drain health and shield within seconds, while having a relative long range, the flames block the players view and it's damage scales with them together with accurancy. Since most of the game takes place in close quarter situations it's hard to dodge them.
The Corpus Elite Crewmen's Flux Rifle use the armour-ignoring Serrated Blade damage type, which means they chew through shields and health very fast. Very fast.
Evil Is Cool: Some players seem to think so towards the Stalker, motivating them to use the coloring options to paint their own Warframes in his colors. Needless to say, some players see his "edgy" style as just a cheap attempt at trying to be cool making this Narm for them.
Potato(es) for Orokin Catalysts and Orokin Reactor, for their shape.
The Stalker is sometimes called Santa by high-level players who farm him for the blueprints of his powerful weapons.
Fridge Horror: Try not to think about the implications of finding Nano-Spores* "Fibrous technocyte tumor. Handle Infested tissue with caution." or Plastids* "A disgusting nanite-infested tissue mass." on Grineer or Corpus units.
Game Breaker: The 'Nova' warframe is widely considered to be wildly overpowered - It has abilities that can, with the right mods and equipment, do everything from one-shot bosses to allow whole groups to bypass agility/parkour challenges to cause all mobs to take double damage from every attack then explode when they die, resulting in a chain-reaction that can kill entire waves at once in defense missions. With proper auras and energy management, it can often spam these abilities for as long as it needs to.
The Grineer Rollers/Grinders. Unlike the rest of the Grineer, which are gigantic, hulking clones, these guys are tiny metal balls that roll around stages at high speeds, turn on a dime, and stun you with each attack. If they come in groups, especially near a Grineer heavy unit, kiss your life goodbye if you don't have an AoE attack primed. One player once observed that all the Grineer would have to do to conquer a planet without sending in troops would be to drop a handful of rollers from orbit and the entire planet's inhabitants would very quickly pack up and leave.
The Grineer Seekers are green-colored soldiers that constantly throw mini versions of Rollers called Latchers. If a Latcher rolls into you, it sticks to you and detonates in a few seconds, unless you dodge to dislodge it. Even worse if you're on a team, as they will shock and disable you until your allies manage to destroy the annoyingly durable and hard to hit thing.
A new addition to the Grineers Goddamn Bats are the Scorpions. Female grineer melee fighters, who by themself are not more dangerous than the standard melee Grineer. What puts them into this category is that they have a 100% hit chance with their harpoon special ability which throws a Tenno to the ground and pulls them towards the Scorpion, and they fire it as soon as they see the player. Since they can even hit players behind walls, it often means they are dragged into the fire of other Grineer.
The Corpus Osprey also count. They have no attack, but project a shield around all their allies and fly around in random patterns making it hard to kill them. They are so annoying that players might charge into formations of enemies just to take them out for the rest of the team.
Corpus Shockwave Moa can knock Tenno down. One by itself is still okay, but when there are multiple it gets worse. Even worse if you're running solo and they stunlock you to death.
Grineer Shield Lancers for the same knockdown reason.
All of the light Infested qualify. Despite supposedly having 'weak' attacks, Chargers will somehow stagger a Warframe with almost every hit and they're fast enough that several can blindside even the most alert of players. Leapers also stagger with their punches but will additionally knock down Warframes with their eponymous leap attack. Runners can't take swings or leap but their kamikaze explosions will stagger all Warframes in a sizable area and they can juggle a Warframe that has been knocked down.
All Heavy Grinner can and will perform a ground pound move when a player comes closer than 7 meters to them. The shockwave will always hit players in that radius and knock them on the back for a few seconds. To make matter worse the attack will always be performed when the animation starts, even when the animation is interrupted and it will always hit, including Tenno who are in the air something not even Shockwave Moas can.
In a Rescue mission, you must bring a hostage to the extraction point to get them off the ship. However, the game doesn't remove the hostage when you reach extraction, so the last thing you see in a escort mission is the hostage watching their saviors board a shuttle and fly away without them.
Melee attacks clip through doors, allowing you to kill enemies that are on the other side.
It was once possible to rescue a hostage by lingering around the brig until the Lotus declared the mission successful and leaving without opening the cell door, making it impossible for enemies to kill the fragile prisoner by any means. This was finally fixed in Update 9.
When the Kogake was first released, it was possible to instantly kill anyone, even bosses, by knocking them down and then standing over their downed form. This was swiftly expunged.
The Kestrel boomerang is able to ragdoll any enemy and throw them several meters back. Since Hek, Regor, Ruk, Kela and the old Golem are basicly recolored standard enemies, they are not immune to the Kestrel's effect. The result is that players can potentialy knock them over into the pits around their arena killing them with just one throw.
Update 9.8 brought a much needed buff to the Mag. It, however, turned Mag's basic - which is only meant to yank enemies close so she can smack them with a melee weapon or execute them with a shotgun - into the Jedi pull on steroids - it would yank anything in front of Mag with an armor-piercing damage of 300 - be it one enemy or an entire room - and kill any non-elite. And elites can just be stunlocked by waiting until they stand up, then yanking them agan.
When downed, you count as stealthed, causing any kills you make to register as stealth kills.
The Heavy Impact mod allows a player to create a damaging shockwave when landing after a certain height. The power and radius of the wave is based on the time spend in the air. Some players found out that sliding down a wall counts as time you fall. As a result running up a 5 meter wall and sliding down will cause a shockwave that can clear entire defence maps.
Mondegreen: The Corpus Worker's Black Speech-inducing helmets often lead to this. A popular one is "MISTER ROBOT!" for the noise they make when they see you.
Female Grineer, too. DEATH TO THE LONGEARS, indeed.
Memetic Mutation: Greedy Milk The community is still trying to figure out what it is. * When siding with Sargas Ruk during the Gradivus Dilemma he would sometimes tell the player that they are going to crush the "greedy milk" from the Corpus skulls.
Narm: Most of the Grineer bosses taunt you with ridiculously flaccid insults and threats.
"Take the 'Warfra' out of 'Warframe', and what are you left with? That's right, ME!"
FASHION VICTIMS ARE ABOUT TO BECOME MURDER VICTIMS~!
The Lotus, in the Operation: Arid Fear preview, got called an "eyeless slag". The update warning included "Tenno, get revenge on the corpus for calling the lotus an 'eyeless slag'."
The new non-English update to the Grineer voiceset occasionally makes the female Grineer sound like The Muppets.
The male Grineer now have the tendency to shout "Tenno SCOOOM!", which is most likely meant to be "scum" however the fact that they constantly repeat it, that it's a normal english word in the otherwise alien language and the way they say it makes it rather silly sounding.
The Stalker, if you aren't expecting him. You're out, minding your own business, celebrating a boss' defeat, when suddenly, the lights flicker. Then:
Stalker: [Player], you cannot run from your past.
The OrokinVoid. Pristine. Beautiful. Transcendant. Utterly empty except for "corrupted," nearly-silent versions of enemies you face in normal levels. No music plays during these levels. Look out a window and all you'll see is black dots in an endless white expanse. It begs two questions - who were the Orokin, and where did they go?
Corpus laser doors. They're SUPPOSED to encourage the party to stick together, but unless you're literally walking in lockstep, they tend to do the reverse. More often than not, the first person through the door will trigger the security camera without seeing it, causing the SECOND person through the door to run head-first into the laser door and take massive damage. Even worse if the second person can't take out the camera from their side of the door and the first person doesn't notice (or care) that they've left their ally behind. Worse still, a player can trigger a camera which will lock in another player in an entirely different section of the ship, with no way for them to take the offending camera out. An update eventually made it so that you can slide past them, but cameras still tend to have the irritating habit of triggering while walking through a door.
Secondary objectives are also annoying. Fought tooth and nail to reach an Artifact and expect to make a mad dash for extraction? Nope. There's intel that needs collecting! The worst of which is that Intel missions tend to be extremely long, especially in big tilesets, like Grineer asteroids. Another classic is having to drag a fragile hostage along on the Datamass hunt. Good times.
Knockdown in general is widely disliked because of the enormous length of time it incapacitates the player for. In a game where you can easily die from 2-3 seconds of sustained fire, being knocked down and unable for move for four or five seconds often results in death. This is made worse because the mods that allow knockdown resistance and improved knockdown recovery are both extremely rare.
Blocking. It has no noticable damage reduction while forcing the player into a slow run, only works against attacks comming from the front, doesn't protect against any effects, including knockdown and drains stamina which would be better used running away from enemies. 4 new mods recently introduced to make it more important again have failed to give it any benefit.
Update 10 initialy had a heavy change to the stamina system. Stamina now had a timer before it would start recovering and would take longer to do so. This was meant to make Stamina more important and encourage players to use stamina boosting mods. However the actual result was that players would be unable to run for more than 10 seconds without stopping to let the stamina recover. After an uproar in the community it was quickly readjusted closer to the original state.
The Corpus Jackal is a fairly easy Warmup Boss. However, it can and will abruptly decide to launch a huge carpet of missiles in front of it, capable of one-hitting even a level 30 warframe - and thanks to the peer-to-peer networks, the attack often doesn't show up, unless you're host. Oddly enough, it stops doing this once it has less than 50% health. The icing on the cake is that it also bypasses several Warframe abilities that are pseudo-godmodes in regular play.
The Corpus Raptor's missiles are much the same, as a single player can only tank it with Overheat or Iron Skin, and Raptor will position itself to bypass other defensive skills if need be. It also has the added bonus of randomly going invincible.
The Corpus Hyena, not so much of a problem when you have partners, but going in solo ill-prepared? Prepare to rage. Armed with instant killing missiles, machine guns that can shred your shield apart in seconds, and constantly rushes you down. Oh and did we forget that its shield can't be taken down unless you hit them in a certain spot and it regenerates fully in almost an instant?
General Sargas Ruk can be a massive pain despite his stated low level. His Reversal Field completely shuts down one player's guns, which makes soloing near-impossible and even a team effort still difficult. He also has a fast-recharging, tough shield, a powerful machinegun and an anti-melee Herd Hitting Attack.
Captain Vor's remake coincided with the release of Nightmare Mode. A bug with his scaling coupled with the Nightmare boosts resulted in level 100+ Vors that could disintegrate a whole squad while barely taking damage. He was reined in shortly after.
The Corpus Raptor, which doubles as a Get Back Here Boss. He flies rather quickly, which makes it impossible to melee him down and difficult to aim at him. He'll snipe you with a salvo of homing missiles that can block your line of sight and absolutely will OHK you and your teammates if you don't have a defensive skill up. Even if that defensive skill was a Snow Globe or Bullet Attractor (the only two capable of protecting your whole squad), he's been known to fly just close enough to unload a missile from inside the barrier or drop some landmines on you. He also randomly becomes invincible. The only way to stop his nonsense is by being Rhino and constantly Rhino Stomping him to clip his wings, if temporarily.
Hek used to be one in the earlier builds when Earth was a mid level area of the solar map. He would move around the arena and always into cover instead of exposing himself to gunfire like most Grineer bosses do. Adding to that his shields had an insane recharge rate, starting to go up again the moment he would not recieve any damage. Meaning players would need to get close to a shotgun wielding maniac with shields that recharge the moment you need to reload. Not to forget that he would spawn decoys of himself making players waste even more ammo. Most low and even mid level players could easily run out of ammo trying to bring him down. He is now somewhat easier but low level players who now reach him earlier can still have a hard time without the right weapon mods. Also thanks to a bug his decoys are now a different color than him, making them easier to ignore.