"Nothing tears us apart. In Greek mythology, the Titans were greater even than the gods. They ruled their universe with absolute power. Well that football field out there, that's our universe. Let's rule it like titans."
In Classical Mythology, the Titans (and their Primordial parents before them) were ancient godly beings that had ruled reality, until they were overthrown by the Olympians in the Titanomachynote The Titans were originally considered true gods. Later Classical writers started confusing them with Giants, but this was not the usual representation. Also, the name Titan sometimes only refers to the first generation, though usually the non-nymph, non-Olympian children of Titans are also called Titans. Titans and primordials have since been featured in many works of fiction, and have several common traits among their varying depictions.
Their other big variable is their morality. This generally goes along with their appearance, for if they look human, they'll probably act human, and if they do look like Eldritch Abominations, they'll act accordingly. Occasionally, a writer may switch the two traits around.
The Incredible Hercules - The Titans and Chronos are imprisoned behind sealed doors, and they break free when the Incredible Hulk accidentally breaks the seal. The exception is Atlas, who is placed at The Axis of the world (center of the world that sometimes moves, changing the political situation of the world, and can also serve as a nexus to all the mystical foundations of the world).
There are also Eternals that live on the moon of Titan, Thanos being the most famous of them. Eternals were always mistaken for the traditional pantheons and those on Titan are no different.
The Titans from the New Titans story "Who Is Wonder Girl?" (one of the earlier attempts to give Donna Troy an actual origin) were absolutely indistinguishable from their Greek and Roman children, falling on the "nice" end of the morality scale as a result by abducting random orphan baby girls throughout the cosmos, raising them to have super powers, then rewriting their memories to forget this before sending them back to their homeworlds (which somehow atones for the whole "eating their offspring" bit from myth). This also subconsciously influenced Donna to suggest the name "Teen Titans" via retcon.
The "aunts" and "uncles" (and presumably, parents) of Luna and Celestia in Under The Northern Lights. They are vast elemental beings which created the world and its intelligent species (learning the latter from the much younger Luna and Celestia when their toys turned into the first ponies because the sisters loved them so much - so yeah, ponies originated as toys of two little girls). The one we have seen in the fic is the water being called Karhu-Akka by reindeer. She combines traits of bear, cow, squid and whale, and now sleeps in the shape of a huge glacier. If she awakes, horrible things will happen. Her rolling over in her sleep when Discord got free is one of the causes for the crisis in the fic, one which might kill all life in a country. Luna, however, remembers her as a kind aunt who played with her and Celestia by the sea and gave them wonderful toys. Their greatuncles and greataunts, however, are pure Eldritch Abomination, seen in a vision as "lights... sounds... patterns of magic in a black sphere that itched the brain and made the soul cry". Discord is one of them.
Discworld's mix-and-match approach to mythology means that while the Gods are mostly Greco-Roman in nature, the Titan-like figures they overthrew are the Ice Giants.
Percy Jackson and the Olympians has the Titans looking almost exactly like normal humans, with the exception of Oceanus. Kronos is possessing Luke and so looks just like him except for having solid gold eyes. The Titans are about as tough as the Olympians, and Kronos is apparently even more so.
The Dragon Crown War has the Oromise who fill the "titan" niche. The oldest intelligent beings in the universe, they were also the creators of many other racesnote creators of everyone, to hear them tell it; the dragons, the second-oldest race, say otherwise and were in general beings of tremendous magical power to the point of being essentially gods. However, they had a falling-out with their closest peers, the dragons, that ended with them getting imprisoned beneath the earth. By the time of the series, barely anyone remembers they existed, and even the eldest dragons can no longer recall what they looked like although Big Bad Chytrine - and possibly her predecessor, Kirun - works to restore them to power, in exchange for magic and arcane knowledge no other mortal possesses.
Live Action TV
In Xena: Warrior Princess, Gabrielle once read a scroll and woke up three Titans, 30 foot giants who repaired the town. The three Titans had a cunning plan to make Gabrielle read the second scroll which would awake 1,000 other Titans and destroy the world.
In Supernatural, Chronos shows up in season seven as a time traveler who needs to kill to control where he can time travel to, and is seeking to get back to his love. An amnesiac Prometheus shows up in season eight.
In Charmed, the Titans are a group of supernatural beings who terrorized ancient Greece and were then imprisoned until the present day. They are certainly powerful enough to be worthy of the myths of the Titans (enough so to scale the heavens and kill almost all of the Elders (angels), but they don't seem to have the kind of cosmic significance you might expect from a creation myth.
Mythology and Religion
The word 'Asura' in Indian Mythology (which includes Hinduism, Buddhism, and several other religions) is usually translated as demon, or "fighting fiend", but in actuality, "Titan" would be the closest equivalent. Their godly counterparts are the 'Devas'.
Inverted in Zoroastrianism, where the 'Ahuras' are the good guys and the 'Daeva' are 'false gods' . It helps to know that the two regions where they were worshiped are neighbors, so it's more a case of opposed cultures and pantheons, than direct succession. There's even etymological & behavioral links between the the Ahura/Asura and the Norse Aesir, further confusing the matter.
Norse Mythology is quite similar to the classical/Greek one. The Jotunn (giants) are basically a mix of the Titans and Protogenoi.
Japanese Mythology: Izanagi, Izanami, and the obscure deities who appeared before them. The obscure deities no longer appear in the universe. Izanami died giving birth to god of fire Kagutsuchi, and Izanagi is too grief-stricken to have anything to do with the world. The current pantheon consists of Izanami's daughter Amaterasu and the rest of the gods in Takamagahara.
At 6'6, when FMW regulars Atsushi Onita, Tarzan Goto, W*ING Kanemura, Koji Nakagawa, Mr. Pogo and others were usually under 6', Big Titan (Rick "The Fake Razor Ramon"/"Ric Titan" Bogner) was a definite Type 2.
In Dungeons & Dragons, titans are a race of outsiders (creatures native to the outer planes) who happen to be about 25 feet tall, so they're not only celestial giants, they are taller than the tallest "normal" giants. Every aspect of them is perfect. In addition, they can cast powerful spells and speak several languages as standard abilities for the race. At a starting CR of 21, a titan with no other skills is equal to an epic-level Player Character in battle. In contrast to their usual portrayals, they're also (slightly) weaker than the gods and act as their servants. They are traditionally Chaotic Good and live on the plane of Arborea (also known as Olympus), though the Greek titans (Cronus, et al) are imprisoned in Carceri (Tartarus).
There are also the Epic-Tier monsters known as Elder Titans, who have more Hit Dice than most deities, more spellcasting levels than most deities in both arcane and divine, have epic spellcasting as the rule rather than exception, and have all-round better stats. They lack the gods' divine salient abilities and maxed HP, but they could definitely throw down with the gods on a similar level, suggesting the above are the younger, weaker generation.
The Primordials (also known as Dawn Titans) of the 4th Edition are a mix of this trope and Elemental Embodiment. The class of creatures known as titans are the Primordials' first creations, who sided with their parents in the war against the gods and in turn created the various races of giants.
In Pathfinder, titans were the first creations of the gods, and half of them rebelled against their creators in the equivalent of the Titanomachy. The giants are their degenerate descendants. The titans who fought against the gods were imprisoned in the Abyss, while those who remained loyal live in Elysium.
In Scarred Lands, the Titans held sway over the planet Scarn, treating it as their plaything, creating and destroying casually as they went. Their children, the major gods, objected to this, as the Titans were laying waste to the world and their worshippers, and went to war against them; since the Titans could not be truly killed, the gods imprisoned and/or crippled the Titans so they could no longer roam free. One Titan, Denev the Earth Mother, sided with the gods, and remained free after the war, bending her efforts towards restoring Scarn. The setting's present day is about 150 years after the war ended, and there's a long way to go before Scarn is healed.
In Scion, Titans are Eldritch Abominations, elemental embodiments of fundamental concepts such as Sky, Fire, Darkness, Time, and Chaos, who are free of human shaping, hard to comprehend, and shape reality simply by existing. The Titans spawned the earliest gods, who sought to avoid being devoured by their predatory parents by anchoring themselves to humanity. Doing so allowed the gods to rise up against the Titans and imprison them; unfortunately, in the last few decades, the Titans have broken free, and once more seek their children's destruction.
Exalted has the Primordials, eldritch beings of vast power who built Creation and then created the gods as their slave janitors. The gods got fed up with their cruddy jobs and had the Exalted overthrow the Primordials (while they stole their bosses' crack stash), but it turns out that killing some of them broke the universe.
The two remaining Primordials, who sided with the gods, are: Gaia (the Earth Mother, creator of the Five Elemental Dragons, who is in some way connected to Creation) and Autochthon (the inventor of Exaltation and the patron of technology, who later fled to Elsewhere and became a planet made of Steampunk). Both of them also happen to be the kindest of the Primordials even prior to the war, with Gaia having an all-encompassing empathy and Autochthon being particularly fond of humans and their skill at technology.
Worth mentioning is that in 2e you can become a Titan yourself, if you're a Green Sun Prince. This means you tie your personal legend into Creation, and exist forevermore barring serious disasters. Since one of the Titans destroyed 90% of Creation back then, the job vacancy of Titan-hood is always open.
In the Role Aids supplement Giants, the Titans were the first giants. They had godlike abilities and powers, including the ability to cast any spell at will, and have artistic abilities that outmatch those of any other culture.
The Titan unit from Age of Mythology: The Titans. In game, Titans serve as the Pantheon of the Atlantean civilization, with Kronos, Oranos and Gaia as main gods, and others serving as minor ones. Barring Oceanus (who is blue-skinned, but otherwise human-looking) and Kronos (who is a giant rock demon), all of them look like Olympians. Furthermore, it's possible for a civilization to summon a gargantuan, city-destroying Titan to fight for them: Greeks have Cerberus, Egyptians have Horus, Norse have Ymir and Atlantineans have Perses. Yes, they took a little artistic license here and there....
Final Fantasy: Titan is an Earth-elemental summon who originally caused a great earthquake to do damage to enemies, but in Final Fantasy VII, for example, he picks up the ground the enemies are standing on, flips it over, and smashes it down. This guy dwarfs half of said game's bosses. The other half aren't dwarfed per se, but they're still smaller.
In God of War, barring those who look like Olympians like Helios, Prometheus and Rhea, all the other Titans are mountain-sized beings that look somewhat human-ish. Some also are Elemental Embodiment(s) like Perses (Lava), Oceanus (Water/Lightning), Epimetheus (Rock), Gaea (Nature) and Typhon (Wind), who wasn't even a Titan in the myths. note In fact, he was the father of all the famous Greek monsters like the Hydra, and was described as a mountain-sized beast with a horse's or dragon's head, writhing serpents for fingers, and wings that stretched across the sky while his arms could scrape the stars. Also, he was the only thing Zeus was afraid of.
Titan Quest: there are the Telkines, eldritch-looking sorcerers with tentacles instead of legs that are said to be remnants of the Titans. In the last part of the game you have to defeat Typhon, a huge four-armored behemoth with tons of attacks.
Titans in Dwarf Fortress are, essentially, ginormous randomizedcreatures spewing things like fire or random disease carrying clouds which can literally be made of anything. They're usually a bitch to kill, as they're immune to traps, temperature (including magma), pain, hunger, drowning, and a lot of other things. This varies significantly with what material, though: ones made of metals rival Bronze Colossi for Nigh-Invulnerability, but you'll occasionally get one made of a liquid that breaks into pieces with a single strike. Forgotten Beasts are a similar class of creature except found underground instead of above-ground.
Rygar has Titans as the main enemies. Some of them are living statues - some of them are apparently little worm-monsters.
In Warcraft Titans are a race of Magitek-using demi-gods who have the self-imposed duty of bringing order to the cosmos. They travel from world to world, terraforming them and populating them with seed races, usually golems or mechanical in nature though they were corrupted by the Old Gods to be made of flesh. After their work is done they depart for new worlds, leaving behind Watchers to maintain any facilities.
Despite their name, the Titans actually resemble Sufficiently Advanced Aliens or Precursors more then any kind of God or Titan. Therefore, they'll be more at home in a Sci-Fi Space Opera then in High Fantasy. Consider that Warcraft and Starcraft share the same core writer...
The Old Gods fit closer to this trope, chaotic beings who sowed the first forms of life on Azeorth, controlled the elements, and were eventually defeated by a new pantheon. Though defeated the Old Gods are not gone and have been working to undermine the work of the Titans and reclaim Azeroth for themselves.
Xenoblade has the entire universe be composed of an endless sea where the two titans stand. These country-sized titansnote Word of God says that they are the size of the Japanese archipelago are the organic Bionis and the mechanical Mechonis. It is said that they waged in battle ages ago, before eventually reaching a stand-still. As the years passed, this lead to life growing in them, and the growth of a conflict between the people of Bionis and the Mechon from Mechonis.
Erfworld was created by the Titans of Ark, who look like giant Elvis Impersonators.