Markiplier (repeatedly dying at the hands of a ridiculous-looking monster):MOTHER... AAAAARRRGH!!! I'm so mad. I'm soOOO MAAAAAD!!! UUUUUEEEAAAAAAAGH!!! NO! FUUUUCKING HELL! I've got a... I'VE GOT A... LET ME OFF!!! DAMMIT!!! DAMMIT, DAMMIT, DAMN YOU TO HELL! YOU SON OF A BITCH!!! YOU'RE DEEEAD! Everything! I hate everything! I HATE EVERYTHING!!! GEDOVAHRDEHRYOUFUCKINGFUCKAHR!!! I'm gonna, I swear... I SWEAR! LET ME THROUGH!!!
A running gag on his Dead Space 3 walkthrough is that he constantly mentions or talks about Ellie's boobs.
YouTube Commenter: After 5 minutes it sounds like some kind of a dark acolyte summoning a demon..
In another video Mark attempts to read a note in the foreign language he quips he accidentally summoned a demon into the viewer's home. In later episodes of the same series he continues to apologizes for it and gives helpful suggestions on how to deal with their new resident.
In his playthrough of the Amnesia: The Dark Descent full-conversion mod Killings In Altstadt, there is a soundtrack bug that causes the background music to be stuck in a loop of a cheerfultropical tune, which is the Shop theme from Ocarina of Time, and Markiplier is forced to play with the bugged music for at least another ten minutes. This eventually drives him insane enough that he tries to kill the main character by jumping off a tall balcony. Repeatedly. While crying.
Becomes especially funny near the end, because the first time he jumps off the balcony, it does stop. And then it restarts all over again. It's like the game was being a Troll to Mark.
During the last segment of Amnesia: Rain, Markiplier thoroughly explains how much he loves meat. And then this slips out:
Markiplier: "My mouth is just watering at the thought of that giant juicy sausage! Ahhh, I can't wait for the flavor to blow in my mouth..."
In Slender: The Arrival, Part 3 when he first encounters the Slender-proxy he repeatedly states that he has a flashlight ("with your name on it!") The actual encounter is very brief, with Markipilier screaming the following: "You're not supposed to do that! You're supposed to be blinded - be blinded, you DICK! THIS IS NOT WORKING!"
When it actually does work on the second try, the normally PG Markiplier breaks out the big guns: "Get blinded, you bitch! Be blinded! Yeah, that's right, suck ten thousand cocks right there, in your EYEBALLS!"
During yet another attempt at the alien surgery, he manages to finally disconnect one of the body parts, and, to his horror, hears it making noises. His commentary beforehand grinds completely to a halt.
At one point Mark loses all hope of winning the game when it gives him the message that 'the fish have been over-fished' and he can only fatten up on berries. He then drives over a pond...and a ridiculously large fish falls into the car. It's so big, it fills up the entire dash and Mark can't even eat it because it gets wedged outside of his reach by some rocks that had fallen into the car earlier.
His Drunk Minecraft series can be full of these. Like this example from the first episode when he his considering getting rid of the webcam, to the others' protests.
Lord Minion 777: Everyone wants to see how stupid you look while you play. *beat* That sounded meaner than it did in my head.
Mark: I will shove a rake up your anus.
Toward the end of the series, Mark, Wade and Bob start getting royally smashed, which culminates in hilarious moments like Mark and Wade goofing around and losing their shit at every opportunity for no reason whatsoever:
Wade: Hey, uh... what's this episode about before we start?
The third part has Mark being so startled by a Jump Scare (namely, the toy soldier shooting Viola with a real gun) that he falls out of his chair and takes his webcam down with him.
All 30 minutes of the "Where Is Wade!?" episode of Drunk Minecraft. A quick recap: Mark and Bob slaughter a village of innocent moon aliens; discover that Wade has been turned into a block of sand; create a railroad to transport Wade's body back to their spaceship; Markiplier goes insane due to having Wade's body in his possession; and they finally make it back to Earth and create a monument to Wade.
The last five minutes of his playthrough of Mental.
His initial excitement when thinking The Curse of Blackwater is a pirate themed horror game, and his angry disapointment when he is told it's not.
Any time where he ends up playing a game that either features a Shout-Out or is directly based off of him in general. One good example is when he plays a mod of SCP Containment Breach... based off of him. He spends a few seconds at the start of the video in stunned silence, and later comments that it brings a new level of disturbing to the game.
When he finally beats the game, his maniacal laughter breaks down into a confused sob.
And then there's his brief Octodad-related freakout at the end of Catlateral Damage:
(smooth voice) And now we know there's more to life (starting to rant) than screaming at a stupid freaking octopus that doesn't know what he's doing and won't ever cooperate with you, (starting to shout) and will never do what you say-
Every time he plays a game where you have to destroy yourself, such as Skate 3 or Turbo Dismount. Crowner goes to this accident, where he manages to get sandwitched between two camions. And he doesn't realize it until he sees the replay.
Tensions ride high however when Crusader JonTron agrees with Wizard Markiplier that Witch Doctor Cry shouldn't call himself a Witch Doctor if he can't even bring Uber back from the dead! I mean seriously, what kind of Witch Doctor has zombie dogs but can't make a zombie Monk? That is ridiculous!
When Markiplier meets Yamimash at Pax on his channel it starts with them dueling in an inflatable american gladiator style battle with Yamimash repeatedly losing Mark rejects his offer of a hug at the beginning pretending to be a heel he then later offers Yami a hand up and and pushes him over his battle stand. However on Yamimash's channel we're treated to Yamimash spotting Mark and eagerly calling out for him. Mark gets lost in the crowd and Yamimash sounds dissappointed until Mark reappears and after a brief discussion Mark pretends to get overly emotional. Then it cuts to the words "Edited Version" The video is shown in a purple tint and saxophones play "I will always love you"
There's a "neckbeard" themed version of Flappy Bird, called Flappy Fedora. In Mark's playthrough of it he spends the entire video doing an impression of MRA/pick up artist types, only to repeatedly get interrupted by the game.
In his playthrough of OFF, Mark scolds the foul-mouthed Dedan after the latter calls the ghosts invading his office "phantoms of shit". Four minutes later, he gets stuck on a puzzle.
"Monacle monacle, tophat, monacle!" Actually, all of Mark's attempts at a British accent. They're massively overdone. Jordan isn't much better admittedly, and slips out more frequently. Mostly because of laughter.
Jordan shooting himself in the foot, complete with laughing fit.
The Call Back to his attempted playthrough of Cold Fusion in his Let's Play of Outlast Whistleblower:
Mark: Those brass, they really like to pump up the atmosphere. This game doesn't rely on a string quartet on my back [as Cold Fusion did every time there was a Jump Scare], just has a guy playing a sousaphone in my ear- (said sousaphone makes its presence known) Stop that, Sousaphone Man!
His moments of Wrong Genre Savvy throughout Among The Sleep, particularly his assumption that the teddy bear is the one responsible for all the horrible things when it's actually the mother. This results in close to every statement the teddy makes making Mark uncomfortable and suspicious.
At one point in his playthrough of It Moves, he makes his character interact with what appears to be a red-faced young girl dressed in a green cloak that audibly growls and stamps a demonic face on his screen, which leaves a faint after-image. It takes Mark two minutes to notice it.
The entirety of his FNaF playthrough is hilarious (well, when it isn't being terrifying), he hurts himself multiple times during the jumpscares, his reaction to Gold Freddy appearing in the security room, at one part he speaks about some of the fanart being produced of the animatronics, and when he unlocks the Custom Night he immediately sets all of the robot's AIs to 20 and dies twice in less than a minute.