Haruhi Suzumiya has something similar with the Data Entity, a non-physical being which created Yuki Nagato in order to be able to communicate with humans.
A fairly unusual example are the Tailed Beasts of Naruto. Each of the Beasts is a mass of chakra guided by a malevolent intelligence, but each one assumes the physical form of a massive, feral beast. When sealed into a jinchuuriki, no body is left behind as it's entirely composed of chakra.
What makes the Bijuu unusual is that their bodies are solid enough to interact with the world. The entire body is composed of "chakra-flesh" dense enough that mortals can interact with and even eat it as in the case of Ginkaku and Kinkaku. However, the energy is volatile enough to kill most people.
The origin story reveals they're fragments of Life Energy from a truly massive Eldritch Abomination. The one who defeated it severed the beast's chakra into nine parts and then imposed the image of a beast on each fragment, likely so they wouldn't merge of their own will. So while they are Energy Beings, they're forced to maintain a physical form.
Digimon can be seen as this, being sentient computer programs, though they still need physical bodies to exist in the Real World. Those bodies are assembled out of nearby elements in a process called bio-emergence. Similarly, humans and any other physical matter is automatically converted to data upon entering the Digital World.
In Psyren people become this when they master the Nova branch of PSI. Asuka teaches this powerful skill to Ageha and Amamiya.
The spirit forms of the Clow Cards in Cardcaptor Sakura, though they usually take the form of humanoids (often, though not always, beautiful women) or animals.
Of special mention is the Illusion Card.
In the Big Finish Doctor Who audio "...ish", the Doctor encounters two sentient bits of language — the Ish, which serves as a singularity of linguistic meaning so strong it warps and destroys all meaning around it, and the Omniverbum, the hypothetical longest word in the cosmos which does the same for reality itself. At one point the Omniverbum chases the Doctor down a hallway despite being fully abstract.
Stardust, one of the recent additions to Galactus' ever growing list of Heralds, already was an energy being before being imbued with the Power Cosmic. In fact, he and his kin were invisible to the naked eye.
The Celestials in the Marvel Universe are composed of a very intense and powerful form of energy — which is intangible and can't do much of anything on its own. It makes a very handy source of energy for the Humongous Mecha that they essentially "wear".
Quite a few appear in Marvel Comics. Two notables are Living Laser, a photonic being made of light, and Klaw, who is composed of solidified sound. Both were human supervillains who got an upgrade into energy beings.
X-Men's Phoenix, originally just Jean Grey with a God Mode power upgrade, was famously retconned into an alien Energy Being after they wanted to bring back Jean but have her not be guilty of mass murder.
And Wonder Man, too (technically he's made of ionized matter, which contains a lot of energy).
Supermanbriefly became an energy being for a reason vaguely explained as overdosing on sunlight. Being Superman, his new energy powers were just as off the charts as his Flying Brick powers. He once magnetized the Moon to keep it from crashing into Earth. He could turn into a solid being though, which was handy for Clark Kent.
All-Star Superman features a brief appearance by things that look like energy beings, but it turns out they actually have some physical presence. Their energy patterns are contained inside some kind of biogenic crystaline structure filled with a conductive gas. In layman's terms, they're living neon signs.
His enemy Hank Henshaw became an Energy Being with the power to possess machines (his preferred form being a cyborg clone of Superman) after exposure to cosmic energy. He's effectively immortal since energy is indestructible. The driving force behind his villainy is his weariness with life and his inability to die. Most of his heinous acts were merely attempts to goad powerful superheroes like Green Lantern and Superman into finding a way to kill him. He once even joined forces with a Omnicidal Maniac cosmic superbeing because it promised Hank it would kill him afterwards.
A subset of this trope, especially in comic books, is the idea of the "man in the can" — the energy being that needs to be kept in a containment suit, lest he lose all coherency and possibly wipe out Detroit. Examples include:
Johann Krauss of Hellboy spinoff B.P.R.D. (and the films of the main series) is composed of "ectoplasm" (a "spiritual energy" similar to Mana) in a containment suit.
Actually, at least according to the (not always internally consistent) cosmology of the Mignolaverse, Ectoplasm is a bit more than spirit energy. The spirit energy still needs a... medium, if you will, to interact with the physical world. This is achieved by combining with fluids from the channeler's own body. Herr Kraus is composed of what was once his own blood, bile, spit &... semen. Yes, that's right, he's basically a walking condom.
Venus Dee Milo of X-Statix is another Energy Being in a bag, though not having a body doesn't stop her from becoming an international sex symbol.
Negative Man from the Doom Patrol has the ability to release an energy form capable of amazing feats, but only for one minute at a time.
Green Lantern villain Parallax is made of... fear, anyway it acts just like an energy being as does Ion (made of Willpower) and The Predator (made of love).
Green Lantern Dkrtzy Rrr is described as a "bio-sentient mathematical equation". Why, yes, it's an Alan Moore creation. Why'd you ask?
Dr. Manhattan from Watchmen sometimes behaves as though he were an energy being, even though he has a perfectly physical body. On the other hand, he doesn't seem to need it too much, since he quickly makes himself a new one after being disintegrated again at the end of the story.
He can teleport, turn intangible, has telekinesis, and can manipulate his own size and color. As the page description says, the definition of "energy being" is pretty complicated, but if this guy doesn't qualify, what does?
E-Man is about an energy being alien who comes to Earth and can turn himself into whatever he wants. Hilarity Ensues.
The Azturi, the unique species created for Kingdom Hearts Keyblade Masters, are an entire race of energy beings. They all look like Genie from Aladdin, except different colors. They're a dying breed, with Gummi (the mentor of the Keyblade Masters) and Genie being the only two Azturi left in the physical world.
Films — Animated
The evil Drej from Titan A.E. appear to be solid beings, but are actually composed of plasma-like energy. This ends up proving handy when they are lured into a trap that siphons away their energy to power the Titan, a ship built to recreate Earth after the Drej had destroyed it years before after an apparently Self-Fulfilling Prophecy warned them that humanity would destroy THEM.
Films — Live-Action
The Darkest Hour is about invisible energy beings trying to suck all energy from planet earth.
In Star Wars, it is possible for certain Jedi to achieve immortality as "Force Ghosts", that's blue glowy energy beings, after they die, their bodies dematerializing instantly in the process. The spiritual techniques necessary for that transformation were discovered by the Jedi Knight Qui-Gon Jinn. The Sith and other darksiders, on the other hand, go for the more ordinary undead ghost forms.
In The Hitchhiker's Guide to the Galaxy series (the books, radio show, towel...), Douglas Adams makes one or two throwaway references to "super-intelligent shades of the colour blue". Color being a form of light, it makes this an "energy being" concept if anything even more bizarre than that suggested for most regular instances of the trope (which may well have been the whole point). Starfish Aliens indeed.
Peter F. Hamilton's Night's Dawn Trilogy features the energy-based hive mind Ly-Cilph, whose evolutionary history the author spends a few pages summarizing. The antagonists of the series, body-snatching souls invading from The Nothing After Death, also seem to be made of energy.
The eponymous character of Stephan King's It generally is portrayed as you cannot grasp the true form. The closest the human mind can come appears in the climax, as a A giant Spider. When Stuttering Bill initiates the Ritual of Chud, "It" flings him through It's mind into a "Darkness beyond the universe", towards where It's true form resides as a swirling mass of Orange Light.
In The Space Trilogy by C. S. Lewis, the eldils are essentially Judeo-Christian angels, or their cousins. They are imperceptible energy beings whose forms exist on a radically different wavelength than ours — for them, gaseous matter doesn't exist, and liquids and solids are gaseous, so the planets of the Solar system are just clouds. To them, light itself is the water through which they swim, and the Sun is their wellspring. "Visiting" a planet means moving into one of those moving clouds and then keeping pace with its orbit to maintain the appearance of standing still, while using some sort of projection to interact with wispy, ephemeral creatures they cannot fully see (ie: us).
His Dark Materials presents its angels as something akin to Energy Beings, being made of a sentient particle known as Dust, which is analogous to RL's dark matter/energy, instead of organic materials. Needless to say that, lacking a truly solid form, they are usually very prone to die.
In Andrew M. Greeley's Angel trilogy, the eponymous angels are immense creatures of (mostly) energy who stand somewhere between humans and God on the evolutionary scale, and willingly act as agents for God.
The eponymous homicidal Catepillar (no, not that kind) in Killdozer was possessed by an energy being.
Piers Anthony used a race of these in OX, mostly as an excuse to toss in references to Conway's Game of Life. No rationale for why a cluster of disembodied energy nodes would work like Conway's cellular automata is provided, but give Piers his credit: at least he tried to base his Energy Beings on something coherent, which is more than other users of this trope seem inclined to do.
Older than Television: The creature in H.P. Lovecraft's 1927 The Colour Out of Space is a bodiless something that's released from the inexplicably colored bubbles in a meteorite and possesses and gradually drains all the life from a farm and its inhabitants. Eventually, the creature gains enough strength to fire itself out of a well and back into space, appearing as a geyser of shimmering alien light as it does so. But then the hero sees a second, weaker entity trying to escape as well, only to tumble back down again. And then the abandoned farm's turned into a city reservoir...
Skewered in The Biology of Star Trek, which points out at least three ways in which these could not exist: their time perception would have problems due to existing at the speed of light, there wouldn't be anything that could hold any kind of genetic code, and any form of sentience would have significant difficulties because all the brains we've encountered have been material.
In The Dresden Files, Bob, Harry's resident arcane supercomputer and magical database, is a spiritual entity composed purely of energy and thought, to the point that simply being exposed to sunlight (which weakens magical enchantments) can kill him outright.
In The Star Dwellers and its sequel Mission to the Heart Stars, by James Blish, humans makes contact with energy beings that are created in the births of stars and look like globes of orange light. We dub them "angels," and as the stories go on, the name feels more and more uncomfortably appropriate.
The "Rakasha" from Roger Zelazny's Lord of Light are the prior native race of the planet that had discovered a technique for "strengthening the flames of the mind that they may burn independently of the body." They can manipulate electricity, among other abilities, and still interact with the material world.
Macroscope by Piers Anthony features an unusual take on the energy being. Near the end of the book, it is revealed that an ancient civilization's members had long ago transferred their consciousness into the interference patterns produced by the reflection the alien signal makes against normal matter. In effect, they aren't even energy, but instead just a pattern floating above an energy field.
The Isaac Asimov short story, Eyes Do More Than See, features energy beings.
The Frederic Brown short story "The Waveries" features probably the most realistic take on this trope, decades beforeStar Trek. The eponymous waveries are literally living waves on the electromagnetic spectrum, and because they are waves, they interfere with technology (making electronics impossible) and are not sentient beings.
Yet another sci-fi trope pioneered by Edward E. "Doc" Smith, whose Skylark Series included the "free minds" One through Seven, who've spent the megayears since their transformation wandering the universe in search of interesting new experiences. Their power is immense - One converts a human into Freemind Eight, then changes its mind and casually conjures him a new body and a starship, accurate to the last cell and circuit, just to get rid of him.
Luke Skywalker and the Shadows of Mindor has an unusual take on this trope in the Melters, who do appear to have matter bodies or a matter medium - a mineral called meltmassif, which is electroconductive - and which perceive the electrical activity in human bodies to be like themselves. Problem is, the meltmassif is completely undifferentiated and doing just about anything to it does not hurt the Melters, and Melters always seek to mix their meltmassif so their individual signals merge. They have no concept of how it's different for others. In the end they are freed from the meltmassif and become proper energy beings... or die. It's Star Wars and everyone is a "luminous being" functioning in a shell of matter already.
Several races in The History of the Galaxy either originally were or evolved to Energy Being level. One such being is implied to be the origin of biological life in the galaxy (maybe even the universe) via accidental Panspermia. The novel quite clearly refers to the entity as "God", even though it's most definitely not immortal and can only exist in powerful magnetic fields of gas giants (in fact, according to the novel, many copies of the being have been created on various gas giants). Another similar race, the Evolgs, similarly evolved when disorganized magnetic fields of a planet became something more coherent. The Emulotti were Human Aliens until they were under threat of extermination by the Shvergs. The Evolgs helped the Emulotti by showing them how to Ascend to a Higher Plane of Existence. At least one human was forcibly turned into energy by an Emulotti machine.
In the sequel to Those That Wake, this is what people in the neuropleth become.
The Feyori from 'Theirs Not To Reason Why'', who live for thousands of years and play intricate games using matter-based sentients as pieces.
Live Action TV
In the Doctor Who serial The Mutants, the natives of the planet Solos have a very unusual cycle of evolution, or something. A year on Solos is 2000 Earth years, and each change in its seasons every half-millennium (with aid from a crystal enthused with thaesium) massively altered the Solonians. Each spring, they were akin to humanoids, while when it turned to summer, the Solonians underwent metamorphosis into energy beings.
So far, though, the trope has been seemingly averted in the new series. The Gelth may look like your typical Energy Beings, but at least they're made of gas.
It was stated in "The End of Time" that the Time Lords planned to become this.
Star Trek has had a bunch of these, including a few which simulated physical bodies — like the Q, the Organians, Trelane, the Calamarain — and at least one group who wanted to get back into physical bodies.
The Vorlons from Babylon 5 appear to be mostly energy beings, although they apparently still have some degree of physicality left, too. In "Mindquake", super-psychic Jason Ironheart, having undergone a Deadly Upgrade, gives up corporeal existence to become pure psychic energy. According to the episode "The Deconstruction of Falling Stars," at least part of humanity appears to be destined to go this way, too, in some billions of years. Note that the far-future human seen in this episode looks like an ordinary man at first, then turns into a cloud of glowing particles which fly into a human-shaped encounter-suit. Similarily, precursor being Lorien is a quite physical humanoid when he feels like it, but can turn into a glowing cloud (possibly his true form) for travelling through space. This suggests that all these beings are basically physical creatures that have gained the ability to turn into a more or less gaseous/plasma/energy form at will.
On Stargate SG-1 the Sufficiently Advanced species "The Ancients" have "Ascended" to a higher plane of existence, resulting in their existing on this plane only as Energy Beings. Daniel Jackson also 'dies', but actually 'ascends' secretly. Twice.
His ascension was only a secret if you call "turning into a glowing ghost-octopus in front of the entire main cast" a "secret".
In "Legacy" Daniel suspects that some dead Goa'uld are not in fact dead but have become energy beings. They haven't, he's becoming delusional because of some alien technology that got into him.
Ironically this later turns out to be exactly the case with Anubis.
In Stargate Atlantis some Replicators try to dispense with their nanite bodies and become energy in an effort to simulate ascension. It doesn't work.
The aliens of Tracker, or at the very least, Cole and Zin. It's never clarified for sure with the others.
All of them are possessing human bodies (except one who possesses a dog). Cole extracts their "essense" and stores it in crystals. It's safe to say that all creatures from that area of space are energy beings in one way or another. In fact, Cole is the only one who manifested his own body based on an underwear ad. The rest took the bodies of people on a train. It's possible that nothing material can pass through a wormhole, so this may have required all the escapees to be turned into energy. All of them still possess their racial abilities (e.g. Cole's hyperspeed and Zin's Telekinesis).
A recurring element of Andromeda is that various celestial bodies have sentient avatars, energy beings who can manifest in humanoid form or as data.
Mystery Science Theater 3000 parodied this with the Observers, who repeatedly claimed to be brains without bodies... despite the fact that they used their bodies to carry around their brains.
In "Counterweight," an episode of the 1960s Outer Limits series, an energy being from the planet Antheon spies on a group of humans who plan to colonize the planet.
Another Outer Limits energy being is the "vacuum cleaner monster" from "It Crawled Out of the Woodwork".
In Power Rangers, Zordon was this in his last two years of life as a consequence of the method he used to free himself from his can. He was still in the can, as it was all that was holding his energy body together, but at least he could have people move the can around for him, rather than being stuck broadcasting to a fixed point.
In Earth: Final Conflict there are the Taelons and the Kimera. The first seem to be primarily energy based but not entirely in the glowing squid squad as yet. The Kimera however look to be entirely energy - except when they feel like it and pretend to be some matter based life form. And the entire being based on energy thing is a key part of the Taelons' story line.
Deconstructed: The Taelons actually burn their energy like any power source in use, and the fact that they have no way of replenishing it makes them an evolutionary dead-end.
This is because they haven't evolved naturally. Taelons and Jaridians used to be one species. Then the leader of a cult (whom the Jaridians view as an Anti-Christ of sorts) proposed draining the rest of the race of most of their Core Energy and using it to keep their group nigh-immortal. The Atavus were already half-energy. The Taelons took that Up to Eleven and screwed over the rest of their species (i.e. the Jaridians) in the process. Even then, the transformation nearly failed. It was only through the influence of the Kimera (whom the Taelons paid back by exterminating them) that they recovered and took on their current form.
The Atavus are half-energy/half-biological. After leaving their homeworld, they found that they needed to replenish their energy supplies on a daily basis. Their energy claws allow them to rapidly drain sentient organics of their life energy. Those who remained on the homeworld didn't have this problem (until the Taelon/Jaridian split, that is).
The angels in Supernatural. For energy beings, they do act very human, though.
All the title creatures of the Ultra Series fall under this category.
The C'Tan star gods are immense energy beings that sustain themselves by draining energy from the stars. The Necrontyr race gave them physical bodies of living metal. They proceeded to turn the Necrontyr into the robotic Necrons and wage war against all living.
The Eldar Phoenix Lords are all implied to be a mix of this and Animated Armor.
The Final Fantasy series, starting with Final Fantasy VI, generally presents Ultima Weapon as an Energy Being. In VI, its self-introduction includes the phrase, "... I do not bleed, for I am but strength given form...", and its Summon Profile in Dissidia says that "[i]t neither harbors nor represents life, but is rather a manifestation of pure power."
The Ethereals, who are essentially goblinsfrom space, embody this trope a bit more; their material shapes are created by wearing mummy-style wrappings and other elements of clothing.
The wisps in the Ultima series are composed of energy and spend their existence gathering knowledge across the various planes of reality. In Ultima Underworld, one can give you a truly devastating spell, Armageddon, which destroys absolutely everything in the game. Including doors and stairways, so that you cannot escape the room.
Every alien character in Mega Man Star Force is a sentient pack of radio waves. By combining with a human, the fusion also becomes a radio being. This describes the eponymous Mega Man as well as every single boss, as apparently mere waves are no match for radio humans.
The character Pyron from Darkstalkers seems to be made from pure energy.
The Thirnovans/Trinovans from Meteos somewhat count. Fine, they're only half-energy, which is also why they apparently only have one form.
Kheldians in City of Heroes. However, they cannot survive for more than a decade as pure energy though so they inhabit organic hosts. Peacebringers and Warshades (reformed Nictus) do this with the consent of the host, the Nictus just take over whichever body they please.
Kheldians (and as a result Nictus) can't take over a body unwillingly though, because the host can eventually just kick them out. However, Nictus get around this by kidnapping them and breaking their will in various ways so that they will become compliant hosts.
The Pkunk in Star Control claim that the Ilwrath used to be perfect beings of shining light, which would seem to fit this bill, before they became too perfect and wrapped around to pure evil spider beings. It's never actually established whether this is actually true, like most of their other bizarre claims or just random Phony Psychic posturing, though.
The Archons and Dark Archons from Starcraft. Affectionately called blue and red balloons respectively by some players, they are made up of psionic energy and are created when two high or dark templar, powerful psychic protoss, merge together. As they lack substance, they're tragically fragile without their energy shields, meaning they may be less useful than the sum of their parts if you're facing an enemy that can deplete shields. Generic archons are made from two high templar, two dark templar make a dark archon, and, in Starcraft 2, two of either templar can come together to make a Twilight Archon regular archon. Interestingly, at least one dark templar, Ulrezaj, knows of a way to become an especially potent dark archon consisting of multiple templar. The result was probably one of the most powerful beings in the Starcraft universe.
Tassadar apparently became an immortal being made of pure light after his Heroic Sacrifice at the end of the first game.
Ulrezaj was a dark templar scholar who found a crystal containing the knowledge to make a powerful Dark Archon. Presumably, he destroyed the crystal after reading it.
Subverted in Jak and Daxter: the first time we see a Precursor, it appears to be made out of glowing blue-white fire. It later turns out that they're instead fuzzy orange mustelids. Daxter was overjoyed.
In Otherspace, the Riftwalkers seem to act as Orz-like 'fingers', as they're extradimensional puppets made purely of psionic energy. Fortunately, they use telekinesis to hold up a shell of dust particles so we can have A Form You Are Comfortable With.
A slight subversion with the Celareons in Conquest Frontier Wars. While they are indeed energy beings, they cannot survive outside containment suits, which are crafted for them at "birth". They, essentially, spend their entire lives in metal suits. Their early stories claim that they were artificially evolved to their present state by an ancient race, who also taught them how to make the containment suits.
The Nebulas in Xenoblade are beings made of pure ether, the substance that builds the world. They tend to be a pain in the ass to fight, having high physical defense and the nasty habit of self destructing once their health gets low.
Xerath from League of Legends was once a man, then ascended to a being of pure arcane energy, then was imprisoned within a sarcophagus for his reckless abuse of magic. Now he is mobile once again, but still not entirely free due to the remaining enchantments placed upon him.
Lambda in Tales of Graces. His actual nature is left quite vague. Basically he's immortal, incorporeal, and living in Richard's head. Or Asbel's, eventually.
In The Elder Scrolls V: Skyrim, the Augur of Dunlain was a brilliant student of the College of Winterhold, who liked to experiment with very deep magic. But one of these experiments went wrong, causing him to transform into an energy being.
Io in Dot A 2 is the very essence of the fundamental forces that hold the world together. In a more meta example, Io's in-game model is purely made of particle effects.
In Portal2 one of the alternate Cave Johnson's in the perpetual testing initiative states that Aperture's experiments inadvertently turned all of mankind into energy beings. He is enthusiastic about this because it brings them one step closer to humanity's ultimate goal... becoming pillar of salt beings.
The Infi-nut from Plants vs. Zombies 2. It's a Hard Light Wall-Nut spawned from a projector which can periodically regenerate itself as long as the projector exists.
In Cookie Clicker, building 15 Prisms unlocks the Rainbow Grandma upgrade, which turns some of the grandmas into photonic beings.
Last Res0rt doesn't state this explicitly, but Efreet are basically Djinn who've sacrificed their bodies for the sake of gaining more elemental powers. They still like running around in their "original" bodies, though...
Spontaneous Combustion has it's main character, Brightly, as a being made of pure light.
In The Gamers Alliance, the Dwellers are beings of pure energy which may occasionally look vaguely like glowing overgrown spiders. They often prefer taking over host bodies from other races in order to interact in the Land of the Living, not caring whether the host body is actually alive or dead.
Star from the Metro City Chronicles is usually content with hurling stellar-fire at people. However, he can also temporarily go full cosmic and turn into an energy being.
Photon of the Supreme Six, a superhero team in the Global Guardians PBEM Universe is an Energy Being whose body is made of pure light. He retains human form mainly because it makes things easier to interact with his teammates.
As an Alien trope, you know there is a Ben 10 example: the Anodites. It's discovered that Gwen herself is half Anodite in Ben 10: Alien Forceand was offered a choice by her grandmother to destroy her corporeal body to become an energy being like her.
Ben 10: Ultimate Alien has a radioactive Energy Being in P'andor. But considering he apparently has DNA to scan (where Anodites don't), it's called into question whether he's really "Pure Energy" or not.
Diagon may look like a Cthulhu-expy, but he's actually an Energy Being. Vilgax defeats (possibly even kills) him by tricking him into attacking an energy draining machine.
In Futurama Amy Wong once tried to set up Leela with M-5438, an entity of pure energy from another dimension that, according to Bender, is "big on musical theater, if you know what I mean".
Another Futurama episode had Melllvar (yes, that's spelled correctly), an energy being who was the living embodiment of the Star TrekFanboy stereotype, and was keeping the original cast alive on its planet. Melllvar borrows mostly from the energy being in the Original Series episode "Metamorphosis", who had fallen in love with Zefram Cochrane and was keeping him alive and young on its planet.
In "A Clockwork Origin", nano-bots planted in a lifeless planet by the Professor undergo Mechanical Evolution overnight, each day being a different level. And the stage right after the "20th Century human civilization" analogue is this.
The members (read: entire species) of the evil Brotherhood of Makuta from BIONICLE have evolved past the need of physical bodies. They still need a shell or armor of some kind however, or said energy will disperse, killing them. Still, being made of energy gives them plenty of abilities, like being able to move into other bodies; and mind-control people with their energies. They have also padded their armor with Protosteel, since there's no body that needs space anymore. This made a painful experience for the Makuta Icarax, as he was devolved into his biomechanical form again by the Mask of Life, making his armor way too small to fit his reformed organs.
One of the latest books mentions the Avohkah, basically sentient lightning living in the universe's core. The Toa Mata drive these things out shortly after being created.
Primus and Unicron from the various Transformers series were originally Energy Beings before being sealedinto planets, which they later took on as bodies. As the Transformers themselves are descended of Primus, they could be also considered such (a Transformer's true self is its "spark," and those can be removed and manipulated), but their bodies are usually much more important to them.
In one episode of My Life as a Teenage Robot, an "energy vampire" called Gigawatt threatens to absorb all of the electricity on Earth. He claims to be a lifeform of pure energy, but after Jenny shorts him out with water from a fire hydrant, he shrinks down until all that's left is his lightbulb-shaped head.
The Meekrob from Invader Zim may be energy beings...when they're not manifesting themselves as giant shoes.
Of course, it needs to make sense even less than anything else in Invader Zim needs to make sense, since they're a simulation created by Zim's Lotus-Eater Machine.
Teen Titans villain Overload is an electric monster controlled by a circuit board. In the final battle, Killowat absorbs the energy and the chip is frozen.
Jonny Quest TOS episode "The Invisible Monster". The title creature was "a mass of energy that somehow came alive".
Star Trek: The Animated Series. In "Beyond The Farthest Star" a being made out of magnetic energy tried to take over the Enterprise. In "Bem" one of these was protecting a primitive species from outside interference.
The New Adventures of Superman episode "The Wisp Of Wickedness". A demon has a laboratory accident that results in a tremendous explosion. As a result he's reduced to a ball of energy with the ability to possess other creatures and make them do evil deeds.
In one of the Zan-and-Jayna episodes of Superfriends, alien bad guys report to their boss, over interstellar picturephone, that the Super Friends are foiling their plans. Their boss casually replies, "I'll teleport you an energy creature." (Said energy creature is less like an Organian and more like a walking molten lava monster, however.)
Many in the UFO community believe that UFOs and aliens are physical manifestations of interdimensional energy beings.