Joe in the the Arfenhouse series was portrayed as a more conventional RPG character with a normal appearance and manner of speaking. He gets a lot of abuse from the various random shenanigans around him, including from Housemaster.
The titular character in Charlie the Unicorn. It doesn't help that the other two unicorns, apart from their blissful acceptance (if not outright knowledge) of all the strange things that occur around them, are really only minor exaggerations.
Among the hosts of DEATH BATTLE!, there's Jocelyn, the team's intern tasked with researching the more obscure information on combatants. Considering the rest of the team consist of a Mad Scientist, a Blood Knight redneck, a narcissisticLarge-Ham Announcer, and a Butt-Monkey robot, she's pretty much the closest thing to an actual normal person among them.
Molly fulfills this role in the Museum Break-In Arc, since she's just a normal (if surprisingly mature) kid locked in a building with an incompetent villain and his legion of minions, an irritable scheming woman with a dumb-as-rocks bodyguard, and a teenage psychiatrist of questionable sanity. But while her voice of reason does help out a lot, she's woefully unprepared for actual combat and needs the help of aforementioned incompetent villain Giovanni throughout much of the arc.
Ramsey serves as this in the Western Arc. Compared to everyone else in Redwood Run, he generally has a clearer eye for reality, frequently pulling back or objecting to Percy and Giovanni's more out-there world views. The bar fight in episode 6 ends up pushing him to his limit though, as the sheer absurdity of the situation is too much for him to handle.
Ramsey: Am I having an aneurysm, what is happening?!
Etra chan saw it!: Azami has to deal with her family (daughter in law included) trying to open a tin can box and is the only major character who's first instinct isn't to open it.
Vaggie serves this role in Hazbin Hotel. Though she was a temperamentalSalvadoranprostitute when she was alive and is currently a bit of a Psycho Knife Nut, she's easily outmatched by the demonic denizens of Hell; her girlfriend and main character Charlie thinks and acts like a Disney princess; Angel Dust is a gay spider demon Drag Queen porn star turned prostitute/mob boss, who loves drugs, alcohol, and violence; and Alastor is The Dreaded, being a nice, charming, powerful, manipulative, murderous demon who plainly states he's only helping because he's bored and finds others' failures entertaining.
Pom Pom is essentially one of the smartest cast members, and often seems to be telling Homestar that everything he's saying is nonsense.
Strong Bad, although he causes trouble, is at least smarter than most of his cohorts (and aware that nobody seems to wear pants).
Strong Sad:
Strong Sad: Look, you can tell me. Homestar: I can't! Strong Sad: Oh come on! What is it? Homestar: I'm PWEGNANT!!! Strong Sad:[pause] No... you're Homestar. Runner. The male. Homestar: Oh, phew! Thought I was apwegnant woman fow a second, thewe.
Marzipan also qualifies at times, although this trait is usually overshadowed by her eccentricity and strawman political zeal. Surprisingly, the Poopsmith is the only character who is always depicted as a rational voice of reason (not literally, of course, considering his vow of silence).
invoked Among the Ultramarines, Chapter Master Marneus Calgar is the only person who seems to have realized that the entire Chapter has been transformed into incredibly bizarre lacking-in-personality Mary Sues who routinely commit Violations of Common Sense.
When we get a peek at the gods' chatroom, Isha and Khaine are the only ones who don't come across as crazy jerks. Of course, the bar to be considered the sanest one when you're in the same room as the Chaos Gods and Gork & Mork is astronomically low.
While she doesn't actually appear in the show proper, a Fourth Wall Mailslot special heavily implies that Inquisitor Amberley Vail was one of the onlyInquisitors in the web series' canon to not return to Holy Terra on the orders of the Emperor when he tried to disband the organization, as she rationally assumed it to be a trick and didn't want to be lured into a trap. This actually follows her characterization in the Ciaphas Cain novels themselves, since they generally portray her as serving as the Only Sane Man for the entirety of the Inquisition.
Spike in the PONY.MOV series considers himself this as revealed in PARTY.MOV where after a long conversation with an intoxicated Pinkie Pie he asks himself "Am I the only sane one in this crazy world of technicolor pony weirdos?".
Churchisn't exactly level-headed, but considering the fact that most of the other regular soldiers in Blood Gulch display varying degrees of incompetence or insanity, he's easily the most down-to-earth character present (being quite possibly the most consistently rational member of the cast even going into the later seasons). While this makes him more proactive than much of the cast, it's also the cause of his endlessly irate disposition that tends to overshadow the otheraspectsof his personality. Though in a twisted sense of Irony, Church is actually the only one of the group that's actually gone insane - Twice, even!
Tuckerincreasingly evolves into this role over the course of the series, usually taking up the role whenever Wash/Church and Tex/Carolina aren't present. Notably, he's the only one of the Reds and Blues to try and poke holes in Sarge'sutterly crazy "time travel through lightning bolt-empowered explosion" theory during Season 3.
Amusingly subverted with Tex. While she may seem pretty level-headed and rational on the surface, it soon becomes clear that her Hair-Trigger Temper and obsessive Greed means that she's ultimately just as crazy as the rest of the cast.
Grifwould qualify in the respect that he's at least as sane as Church... were he not so utterly apathetic to the crazy goings-on of Blood Gulch. Witness his logic in the Warthog argument in the series' second episode, which is of course completely shot down by Sarge as being insane and made up. How much of his resulting personality is Flanderization or him just realizing that he cannot make a difference is debatable.
Simmons has also shown himself to be fairly rational when he's not being a sycophant. One could make the argument that the position of Sane Man among the members of Red Team rotates depending on whether or not Simmons is sucking up to Sarge.
Lopez the Heavy acts as this to the Reds and the entirety of the Blood Gulch Crew in general. However, because his programming results in him only being able to speak in Spanish, his attempts to bring order and logic to his team are either ignored or misinterpreted.
Agent Washington from The Recollection and onward ultimately fits into this trope the best out of the whole cast. It actually creates a weird dynamic where Church mocks the others for their stupidity and Washington then mocks him for the same thing. Again, however, it should be pointed out that in a show where pretty much every single member of the cast is either crazy, an imbecile or both, "Only Sane Man" is a pretty relative title. Wash is most assuredly not normal, but compared to everyone else, he's at least mostly all there. In any other fandom, he'd be likely considered a nutcase.
Upon completing his Character Development in Season 10, Wash truly becomes the Only Sane Man, to the point he even calls Church out on his Jerkassery (which actually helps incite further development and introspection for the latter).
After she learns to let go of her fervent desire for Revenge, Agent Carolina starts to fall into this territory among the Reds and Blues alongside Wash. While she does still have her own Not So Above It All moments (just like Wash), by Season 15 it's clear that she and Wash have essentially become the sensible Team Mom and Team Dad for the whole Blood Gulch Crew.
Darkly subverted with Counselor Aiden Price of Project Freelancer. While he's probably the one person who most closely assists the Director with his nightmarish and unethical acts, he at least voices objections whenever the Director does something particularly dangerous, cruel, or just plain insane. The Director always overrules him, and he ultimately always goes along with it, though. It's also subverted in that he's clearly not all there upstairs either.
There's an interesting case with Locus during The Chorus Trilogy, as while he's a Shell-Shocked Veteran who is clearly not all the way there, he's still the most level-headed and logical out of Charon Industries' mercenaries on Chorus and often has to drag both Sharkface and Felix back on track so as to keep them focused on their mission.
Trick Moon: Prince is the the only one who takes protecting the Moonstone seriously while his younger siblings tend to be too focused on having fun to care unless it's actually in danger.
Turnabout Storm: Much like in their home series, Phoenix Wright and Twilight Sparkle play this role in different ways: Phoenix comes from a mostly realistic setting full of quirky characters, and now has to cope with the weirdness of Equestria plus a new set of quirky characters, while Twilight is the most sensible pony in Ponyville and a constant voice of reason. Much inner snarking ensues with them.
has to deal with her family (daughter in law included) trying to open a tin can box and is the only major character who's first instinct isn't to open it.