Skeleton Warrior

Skeleton Warriors or simply Skeletons are some of the most basic enemies found throughout fantasy games, novels and yes, table-top games. In most settings they sit somewhere between chaff and meat bone shield, with them typically being one of the most basic enemies you can throw at a party/protagonist/opponent, though in some settings they can prove more formidable adversaries.

There was also a Science Fantasy cartoon series in the early 90s (when else?) called "Skeleton Warriors" and it was metal as fuck, with heroic knights battling a band of evil warriors who had attempted to seize a magical artifact, only to be transformed into ghastly living skeletons with dark magical powers. Like most 80s-to-mid-90s toons, it had an awesome theme song. You can check it out here.

DnD

The Skeleton Warrior was a short-lived creature in the days of Advanced Dungeons & Dragons, appearing in the Fiend Folio. Created to make up for the fact that monsters couldn't "level up" the way adventurers could in those days, the Skeleton Warrior exists to keep the skeleton relevant for longer.

Fluff-wise, a Skeleton Warrior is an undead Fighter of considerable level, brought back from the dead as an intelligent, self-aware skeletal undead by an evil necromancer or demigod, who controls them by trapping their soul in a golden circlet. This circlet can be used to control the Skeleton Warrior, but it will always be watching for a chance to turn on its master and kill them; only by obtaining the circlet can the Skeleton Warrior's soul be released to the afterlife.

Standing as an interim step between skeleton and Death Knight, Skeleton Warriors are extremely tough. Their weapons hit as if they were +3 weapons, they are immune to non-magical weapons themselves, and they have a 90% resistance to magic spells. They exude an aura of fear that causes any creature with less than 5 hit dice to flee at the sight of them, and they are immune to clerical turning effects.

The Skeleton Warrior's legacy lives on mostly in the Skeletal Champion template for Pathfinder.

A skeleton warrior named Dekion appeared in an early episode of the D&D Cartoon.

Warhammer Fantasy Battles

For the various necromancers of the Old World, skeleton warriors are the typical front-line troops for most of your armies. With the exception of the Vampirates, who are almost entirely zombies. All other Undead factions typically use the skeleton warriors or their more elite counterparts. Mostly because it's easier to get long dead people than recently dead people in the form of zombies, and because skeletons don't have any of the residual personality left like mummies do. (With the exception of Dwarf skeletons who are as stubborn in death as they are in life, leading to many a poor necromancer dying at the hands of pissed of skeleton dwarf slayers.)

As you would expect, the Grumpy mummies and the Hot-topic fans use them differently due to the different areas of the world they inhabit.

The End Times made it so both versions could be taken in the same army, the Undead Legion.

Tomb Kings

Do not awake what sleeps beneath the sands...

In the New Kingdom-themed ranks of the warriors of Nehekhara, Skeleton Warriors are the mainline infantry to be found supporting both giant constructs and their masters in the deserts of the far south. There, rows upon rows of generations of warriors will march into battle, willing to die a countless number of times for their God-kings, as they have swore an eternal oath of loyalty before the gods of Nehekhara, which they intend to carry out.

Unlike the skeleton warriors of the vile necromancers to the north, the Skeleton Warriors of Nehekhara all pledged themselves willingly to their king, and are not mindless automata before them. Instead, when their king died, they would be lead to grand caverns and courtyards before the pyramid by their Master in Arms, and caused them to stand perfectly still and in rank as heavy boulders blocked all light from view and hot sand filled above their standard pole, suffocating them to death, only to awaken once the Great Necromancer's curse filled the lands of Nehekhara with necrotic energies, raising them once again to heed the call of their kings and Liche Priests, once again calling their souls back from the Realm of the Dead to be bound to their now decayed bodies, no longer able to fully remember the life they once had as well as their mummified leaders. However, they will always remember their undying loyalty to their king with perfect sincerity and clarity, as well as their devotion to the Gods.

The Skeleton Warriors of the Tomb Kings not only have more experience with their khopeshes, spears, and maces then almost any living creature, but also carry shields and banners showing archaic symbols of their devotion. Though they no longer carry lungs, their war horns still sound just as loud as they did in life. None break rank, except to gather the bones of their fallen comrades so that they may rise once again should their king fall and need to be resurrected. With no fear, pain, nor fatigue, skeleton warriors will continue to fight until they crumble to dust, no matter how overwhelming the foe or how impossible the odds. They know not mercy, only that they must obey their king's decrees to the letter and with no hesitation. Thus very few mortals are able to fight them in the unbearable Nehekharan sun without fleeing in terror or fainting outright, but those that do will find they are not particularly strong, but their numbers make them indomitable.

Vampire Counts

Skeletons usually congregate around suitably spooky locations.

In the crooked and corrupted lands east to the Empire rule the Vampiric aristocracy only known as the "Vampire Counts," who control large hordes of undead puppets. Aspiring Necromancers will often study here, only to return to the Empire or Bretonnia with dark knowledge they wish to use to further their own goals.

Most cemeteries in the Old World are protected by Morr, the God of Death, who guides souls to the afterlife and away from predating daemons and necromancers. It is his priests who give rites to the dead to protect them from such desecration, and so many in the Empire may sleep easy at night knowing that their own loved ones won't come back to murder them through the whims of a depraved fool.

There is one issue though: Morr hasn't been around forever, and there will always be those that die whose bodies are never recovered or found, especially in battle. And so the corpses of the long-dead barbarians who used to raid and plunder before the time of Sigmar Heldenhammer that covered the lands of the empire are the prefect picking, using rusted iron weapons and decayed wooden shields, the dead from this era are prefect pickings, as their spirits are bound to where they lie, unable to find peace due to the brutality of their deaths and the inability to attain proper funerary rites. Dark Magic is often drawn to these areas and so a magically sensitive individual who knows where to look can always find these bound souls and corpses to use as cannon fodder, and if they are able to successfully cast their spells without summoning...unwanted attention...the dead will emerge from the sepulchers, clawing from beneath the dirt and standing in formation, ready to obey orders, their empty, soulless sockets flickeringly faintly in the moonlit sky with some vestigial personality, all but gone now. Faint memories and tactics of the past may make themselves known, but will disappear as soon as a new order is given by their new master. There is no autonomy nor intelligence in them, and they are but literal puppets before the might of the Vampire or Necromancer who has summoned them, with no mortal drives like hunger, fear, rage, or sadness to drive them, only the ever-present, undying will of their master.

It should be noted, If the Magician fucks up, there's always a chance he will be killed by his own creations, who will go on to raid and pillage indiscriminately and without control.

Although there is no flesh nor muscle to keep the skeletons together or from falling apart, they are able to move through necromantic energies and power in the wind of Dhar to act as ligaments, sinew, muscle, etc. that can let them act. Unfortunately, this magic is fragile at best and though bones can deflect and take a lot of damage, a proper sword strike, arrow, bullet, cannoball, etc can disrupt the magic and damage its shell to release the binding and cause the soul possessing the skeleton to be released, finally free to move on to the afterlife...That is, until a necromancer raises their bones once more. Even skeletons bludgeon with a hammer, mace, or who have had their spines snapped into pieces may raise again so long as the Necromancer has the necessarily skill and ability to control them, meaning that if the necromancer is powerful enough, some spirits may never know anything but undying servitude to a grisly and undead monster.

Vampire Coast

The Vampire Coast surprisingly doesn't use skeletons, and instead focuses almost entirely on zombies. It's likely the mix of ship-wrecked sailors, washed up bodies, and people caught in a very bad raid mean that they typically don't get things who have been dead for long, especially with the various predators and scavengers of Lustria and the sea eating anything that won't put up a fight. Additionally, corpses will float, whereas skeletons typically sink to the bottom of the sea, which, as you would expect, would make it hard for an entrepreneurial Vampire to get his hands on, due to the unknown eldritch horrors that lay at the bottom of the Warhammer World's seas. Some skeletons may be found on Necrofex Colossus, but overall they are basically non-existent.