Oculothorax

A subtrope of Cephalothorax, Oculothorax is a term used to describe a character's body that is primarily an eyeball. Common variants include a character made of several smaller eyes around one giant center eye or a single eyeball above a wide mouth. A third common variation is a single disembodied eye with a pair of demonic wings. These creatures will generally move by simply floating in the air like a bubble if wingless. If they have limbs, they tend towards tentacles or wings rather than arms and legs. May attack using special eye-related attacks such as petrifying gaze or Eye Beams. Because of the symbolism between disembodied eyes and evil creatures like this are more often evil than not. It is also a good way to make them appear truly alien.

The name comes from the Latin oculus ("eye") and thorax ("chest").

Anime and Manga

Suezo from Monster Rancher is this.
Medama-Oyaji from GeGeGe no Kitaro
One of Demon Detective Neuro's 777 Tools of Hell is Evil Friday, a swarm of little eyeballs with legs that he can see through. While most commonly used for research, reconnaissance, and tracking, they're shown to have lives and personalities of their own, and one memorable aside shows that they enjoy participating in racing. Why Evil Friday? Who knows?
In the Tokko manga, Kureha keeps a little pet phantom in her jacket pocket that is basically just an eyeball with legs.

Comic Books

Doctor Strange's enemy Shuma-Gorath has no true form, but he prefers a six tentacled, starfish-like form with a single giant eye.
- A post 2000 pre 2010 X-Men comic book introduced us to a disciple / cousin of Shuma-Gorath which is a six tentacled, starfish-like form with many eyes. They have a fight. Triangle wins.
Similarly, Starro, a Justice League of America foe, is a starfish with one big eye in the middle or at least, post-retcon, his drones are.

Film

Big Trouble in Little China had a Beholder-like monster.
The aliens in It Came from Outer Space.
One of the monsters in Voyage Into Space was a giant floating eyeball.
The Mad Scientist in Freaked had, as his trusty lieutenants, a pair of Rastafarian, machine gun-using eyeballs the height of a normal person. The inherent flaw of such a guardian became apparent when the hero discovers how well A Handful for an Eye works on someone who is all eye.

Literature

Discworld has Bel-Shamharoth, the fact that he has the giant eye bites him on the tentacled butt.

Live-Action TV

Early Mighty Morphin Power Rangers monster Eye Guy is built entirely out of eyeballs. His "Core" form is a single Eyeball floating in the air, making him this.
The Atraxi in Doctor Who "The Eleventh Hour" is nothing except a giant eye. Check it out.
Beljoxa's Eye in Buffy the Vampire Slayer is a...thing made of several eyes.
Pee-wee's Playhouse once hosted Roger the Monster, a big eye with a mouth underneath, all attached to a foot-like body. Although friendly, it made few appearances, probably due to the prop's cumbersome nature.

Tabletop Games

The Beholders of Dungeons & Dragons are the Trope Codifier for this type of monster in fantasy settings.
- The Eye of the Deep: An underwater Beholder-like creature with a large central eye that sends out a blinding flash of light that dazzles and stuns its victims.
- Floating Eye: A fish with a single large eye that hypnotizes its target.
- Eyewing: A creature of the Abyss with bat wings and an 8 foot long rat's tail. Has a 4 foot wide eye that weeps an acidic, poisonous blue liquid. The liquid forms into a 1 foot diameter sphere when the Eyewing drops it on its target below.
Magic: The Gathering has the Evil Eye of Urborg. The Evil Eye of Orms-by-Gore appears to be related, but the artwork is zoomed in too closely to see its full body.

Video Games

One of the monsters in Conan: Hall of Volta was a large floating eyeball. You can see them here.
The 'Eyeball' costume in the Costume Quest DLC 'Grubbins On Ice'.
The Wise One in Golden Sun.
Mr I from Super Mario 64 is just an eyeball.
The Ahriman in Final Fantasy games.
The Pain elementals and Cacodemons from Doom.
EverQuest 1 and 2 and has the 'Evil Eyes'.
Shin Megami Tensei has several, like Ichimokuren.
A betentacled floating eyeball early boss in Raidou Kuzunoha vs. the Soulless Army.
Ameno-Sagiri, a giant laser eyeball boss from Persona 4.
The Feyesh in Super Smash Brothers Brawl, an eyeball fish with tentacles. Yuck.
Stalkers in RuneScape
A Link to The Past: the Dark World's Goddamned Bats are eyeballs with bat wings.
- And Adventures of Link has some flying eyeballs. Incredibly annoying flying eyeballs. Some of which are invisible without the right item.
- The "Ocular Parasite" boss in Skyward Sword, which is four giant eyeballs on stalks, and a fifth giant eyeball with a mouth and wings, also on a stalk.
- Vaati, the boss of the The Legend of Zelda Four Swords games, generally takes the form of a giant eyeball with 4-6 bat wings.
Suezoes from Monster Rancher are naught but eyeballs and mouths on a single tiny tail/foot-like appendage.
Charade, of Soul Calibur, is a humanoid with an eyeball for his thorax. He still has a faceless "head" too.
Overlord has beholders that teleport enemies into combat, as well as projecting an energy field directly below them that vaporizes minions and inflicts heavy damage on the Overlord.
The (very low-level) Aibatt mobs in Flyff.
The MARDEK series has several floating eyeball monsters, most of them Palette Swaps based on element, but in a bit of a twist they each usually have a "polyp" form as an eyeball stuck to the ground with a stem that is explained to eventually grow into the floating eyeball form.
Many of the bosses in the Kirby series are like this. In no particular order, there's Kracko, Dark Matter, Dark Nebula, Zero, Zero-Two, Drawcia Soul, and Dark Mind's second form.
Small, medium, and large in Terraria: Servants of Cthulhu, Floating Eyes, and the Eye of Cthulhu.
The MONOCULUS! from Team Fortress 2.
The Oculons in Ascendancy (although like most of the other examples here, they're a race of chivalrous astronomers, rather than being evil or otherwise disturbing.)
Subverted with Roggenrola from Pokémon. What looks like its eye is actually its ear.
The old Might and Magic verse had Evil Eyes/Beholders, who are heads with a single giant eye floating on tentacles, optionally with additional eyes on eyestalks. They were created by a mad mage to serve as living weapons, and do well in that role, even if they hadn't entered service by the time the war they were made for ended.
Devil World has Medaman, who thanks to a Japanese Visual Pun turns into a fried egg when defeated by fire breath.
"Floating Eye" demons in World of Warcraft. (The model's file name is "beholder.")
Monoeyes from the Kid Icarus series are exactly what they say on the tin.
A common enemy in the Castlevania series are "flying eyes".

Western Animation

Dr. Zin's Robot Spy from Jonny Quest is a robot composed of giant eye on spider legs.
- Several more of them appear in the Jonny Quest the Real Adventures episode "The Robot Spies".
- Another example from the original Jonny Quest: The title creature in "The Invisible Monster".
In The Venture Brothers, Doctor Venture builds a robot that's almost identical to the Robot Spy as one of the series' many Shout-Outs to Jonny Quest. It is later used as a new body for H.E.L.P.eR.
ReBoot features this as a sprite in one of the games. A single eyeball that uses its nerves and veins as limbs, like an octopus.
From Monsters, Inc.: Mike Wazowski, who is mostly a giant eyeball, with a small mouth and spindly arms and legs.
The Eye from 12 oz. Mouse is a giant eye with legs and a mouth. Other characters comment on how gross he is.
On an episode of Regular Show, Benson hires one of these named Peeps to watch Mordecai and Rigby to ensure that they don't slack off.
William, a character from The Amazing World of Gumball, is an eyeball with wings.
Futurama: The crew comes across one acting as a sentinel in the Central Bureaucracy HQ. It's sleeping, they slip past it, and the thing starts whining about its supervisor.
The Powerpuff Girls fought a beholder-like creature made up almost entirely of eyes in the Season 3 episode "The Mane Event."