52: Every issue had pencil layouts done by one artist, Keith Giffen, in order to keep this trope to a minimum. However, there were still a few minor slip-ups, the clearest example being Renee Montoya and Kate Kane. They were well-endowed but realistic when they first spoke to one another (They were still gorgeous, but it was manageable), but when they met in the park in the next issue they were both bulging out of their tops. The commentaries usually passed it off as exactly this trope, and not a deliberate attempt to titillate readers.
Animal Man: The emblem on Animal Man's chest can either be the letter A or an arch shape that merely resembles an A. The shape of his goggles also seems to vary.
Aquaman: In Aquaman: Sword of Atlantis, depending on who's drawing him, Arthur looks anywhere from his late teens to being middle-aged, with the only concrete evidence of his age being "younger than the first Aquaman."
Black Canary: Is Black Canary a natural blonde or not? Traditionally she's naturally black haired but either wears a wig (pre-1990s) or dyes/bleaches her hair (post-1990s), but some artists have depicted her as always being a blonde.
In series after the original Arnold Drake run, Cliff Steele/Robotman would be lucky if his robot body would keep a consistent design for longer than a few issues.
Dorothy Spinner had several notable discrepancies in her physical appearance that changed depending on who drew her, such as whether she wore her hair in pigtails or wore it down, if she wore a blue and white dress like her literary namesake Dorothy Gale or went with less feminine apparel and the severity of her ape-like deformities (one example being when Erik Larsen, Doug Braithwaite and Tan Eng Huat drew her with a high forehead and a prominent brow, features which were eschewed by most other artists who drew her).
Etrigan: Etrigan's height, facial features, and outfit vary wildly. Most artists draw him medium height with a mostly humanoid face and a Primal Stance, but when he guides Dream through Hell in The Sandman he barely reaches Dream's shoulder and has an elongated reptilian snout, and in Swamp Thing he has a harelip. Then there's the endless variations in which way his horns point, what his bracelets and belt look like, and how much leg he's showing. In a subtler example, nobody can decide whether Jason Blood's skunk stripe is on the right or left side of his head.
Green Arrow: Another notorious entry for Ambiguously Brown; Green Arrow II, Connor Hawke. He's supposed to be 1/2 white, 1/4 African-American and 1/4 Korean. Good luck finding an artist who can draw it. Even his skin is wildly inconsistent, as some colorists depict him with a dark complexion to reflect his mother’s African heritage, while others have him looking just as pale as Oliver Queen, his white father.
How the Green Lantern energy aura looks. It's either similar to electricity (Seen on the New 52, mostly), to fire (Seen on the Alan Scott Lantern), to plasma (Seen on Rebirth), to just light. Similarly, sometimes Lanterns have a natural glow around them, or their rings emmit a constant flux of energy, while other times they don't need it and it's more of a conscious choice they do. Guy Gardner canonically has so much willpower than his ring is constantly emanating sparkles because it can barely contain it, but that doesn't stop even rookies from having energy leaking from their rings.
If the rings project a second Lantern symbol above the Chest Insignia and the ring tends to vary too, usually being the case in comics from the New 52.
The Human Lanterns' eye colours. Are they green because of the rings, naturally green, or not green at all?
Does Larfleeze look more like a pig, more like a horse, or even a Baphomet-like demon?
Does G'nort look like an anthropomorphic dog, or Barf from Spaceballs? Likewise, does Ch'p look like a realistic chipmunk or something out of a kid's cartoon?
Sinestro's skin; Purple? Reddish? Magenta? Pink? DOTA. And to a lesser extent, whether or not his ears are pointed.
Not just his ears either, but also the shape of his head. Some artists (and animators) give him a normal "human"-shaped cranium, others endow him with an exceptionally tall forehead (like a less-extreme version of Hulk villain The Leader) that goes straight up, while others still depict more bulbous proportions, with a subtle outwards flare. His resulting hairstyle varies as well, from nondescript short hair, to a pronounced widow's peak, or even a flattop (in Emerald Dawn II). From the advent of forming his own Sinestro Corps he's been sporting a much shorter hairstyle with a shaved undercut befitting his "fascist" look (note the Naziesque armband), to which most artists have since adhered.
Curiously enough though, other Korugarians are almost never drawn with non-human ears or cranial shapes, including his direct blood relatives.
Although fellow Korogarian (and Sinestro's daughter) Soranik Natu usually stays a pretty steady shade of pinkish-purple. This is probably because she (a) hasn't been around nearly as long and (b) only really appears in the Green Lantern books.
Hank Hall/Hawk's build has varied from being simply brawny to full-on Liefeldian beefiness (it doesn't help that the '80s mini-series was drawn by Liefeld to start with).
Artists also waver between showing Hawk and Dove's eyes through their costumes or doing a full-on Batman effect with whiting out their eyes.
Dawn Granger/Dove II started out as an average-height girl who would magically grow to become taller as Dove, while her shorter blonde hair would change to become long and white. In recent years, artists often forget this and portray her height as being the same in both forms and her hair winds up often being colored white in civilian mode too.
Holly Granger/Hawk II: A shorter woman with an average-sized chest or a practical Amazon with large breasts? Was her hair super short, shoulder-length, or was it down past her waist? Her hair color was another variable: Originally Geoff Johns and Mike McKone considered her as a blonde, but changed their minds and had her with pinkish-red hair in her debut (though the colorist forgot to recolor her hair in one panel, leaving her as a blonde). Johns' official profile for her in a Secret Files issue then stated that she had brown hair, yet his draft for the first One Year Later Teen Titans issue described her as a redhead. In her sporadic appearances during her tenure as Hawk, colorists seemed to shift between all three of those colors for her hair, sometimes even in the same event (World War III).
Jonah Hex: The extent of Jonah Hex's scarring varies greatly between artists. He's always got the mouth-string, bug-eye and perma-sneer, but some artists draw him with only those, most artists add some burn scars (The Movie seems to have gone this route) and some artists turn him into Two-Face in a cowboy hat.
Justice League of America: Doctor Destiny got subjected to this during the late 1980s and early 1990s. The appearance Destiny has outside of these? Despite predating the character, you can be forgiven for easily getting Dr. Destiny mixed up with Skeletor.
The original penciller for The Sandman (1989), Sam Kieth, depicted him as completely bald and with horribly rotting, seemingly dripping skin. When Mike Dringenberg took over pencilling duties, Doctor Destiny acquired side hair and lost the rotting skin.
Batman Vol. 1, #492, the first proper part of Knightfall sees Destiny among the inmates listed who escaped during Bane's attack on Arkham Asylum. The late Norm Breyfogle, who drew the issue, went with the McKean/Kieth/Dringenberg depiction with a shriveled face and tufts of hair.
The "Destiny's Head" arc of Justice League America, where it was revealed the Bloodwynd who originally joined the League was really the Martian Manhunter, saw writer/artist Dan Jurgens mix the classic skull face with the long side hair of Dringenberg's depiction.
Cyclone's costume is pretty hard to draw, so various artists raise or lower the slit on the side (or remove it entirely), alter the amount of strips on the leggings, change the size or colour of her emblem, and change how baggy or large the overhanging pouch is.
In The Lightning Saga, a Justice League and Justice Society crossover, the third Wildcat suffered heavily from this trope. When drawn by the JSA artist his musculature was defined but lean, especially when compared to the body of the first Wildcat (his father and a heavyweight boxing champion). But whenever the JLA artist drew him he would suddenly have huge muscles that easily rivaled or even surpassed his father's. This actually becomes kind of funny when reading the trade paperback, since the artists alternated on chapters and make it look like Wildcat II is constantly expanding and contracting.
Artemis Crock's (Tigress') hair changes shades often. It has been various shades of blonde and even light brown.
Lobo: Lobo, at least before Simon Bisley's despiction of him, had his hair and black facial marks (specially those on the side of his mouth and chin) vary a lot.
Martian Manhunter: Everyone is agreed that the Martian Manhunter has red eyes, but their appearance varies depending on the artist. Most of the time they are pure red, with no iris, pupil or 'whites'. Sometimes they have these structures, but colored in subtly different shades of red. Very rarely they will look like human eyes, but with red irises. This variation can be explained by the fact that J'onn is a shapeshifter, which lets the artist off the hook.
Go back before the 2000s, however, and there're comics where J'onn's eyes are solid black. At some point, the red eyes won out decisively, and the black eyes haven't been seen since.
Sometimes all the characters are drawn in a unified style, sometimes Billy/Cap are drawn in homage to C.C. Beck's original cartoony Black Bead Eyes style and the others in a more realistic one.
Freddy Freeman, apart from his New 52 Adaptation Dye-Job that took away his young-Elvis look, has used a variety of mobility aids and had several Limited Wardrobe redesigns more radical than Billy's, some more self-consciously rockabilly-inspired than others.
Black Adam was originally drawn with pointy ears for some reason. When he was introduced to the DCU in The Power of Shazam!, he had normal ears. When that version of Adam appeared in Justice Society of America, he had pointy ears again. Since then it seems to be entirely down to whether the individual artist thinks it looks cool or silly.
Some artists will go out of their way to draw Shazam as an adult version of Billy.
Vixen: Vixen has an odd one in how her powers are presented; she has the ability to take on the abilities of any animal, but DOTA, there may or may not be an aura looking like said animal around her when she does it.
