Ars Magica: Lycanthropy is the result of a curse which can be magical or faery in nature, and is tied to the moon cycle. If taken as a blessing, transformations can be controlled. Were-bears and were-lynxes are also possible in the setting.
Deadlands: In the Classic Collection, the DuPonts are a branch of the mad Whateley family who are known for being werewolves, as well as inbred mad magicians. Mina Devlin has a few of them working for her at the Hunt-Phelan house.
Werewolves have always been able to take on the normal wolf form and infect with a bite, but other details have cropped up with the evolution of the game, including the addition of a "hybrid" form equivalent to the Man-Wolf, the existence of natural lycanthropes in addition to infected ones, and the imposition of a whole new alignment (and personality) not just on the nonhuman forms but on the human(oid) as well. The game later inversed the process with the wolfwere (and subsequent varieties of beast-were), who is an evil, intelligent, shapeshifting wolf who assumes a human form to mingle in society and lure potential victims. Werewolves and wolfweres both share intense loathing for each other.
In 2nd edition, there was also the seawolf (an amphibious werewolf that could take the form of either a water-breathing man-wolf or a giant wolf-headed seal) and the loup de noir (a "skinchanger" werewolf who assumed wolf form by donning an enchanted wolf's pelt).
Mystara: The Basic D&D supplement Night Howlers gave Known World weres of all stripes the in-detail treatment, including rules on using them as player characters. Newly-infected weres would generally start out much weaker than their default "normal monster"-level cousins and had to earn experience in beast form to get the full range of abilities, but could also eventually end up considerably more powerful (including eventually acquiring the hybrid "beast-man" form at suitably high level). The book also justifies the infectiousness of lycanthropy by making the cause of it an explicit magical virus that escaped from an Alphatian laboratory involved in shapeshifting research centuries ago and mutated into a number of distinct strains as it spread.
Lythari, originally described in a a Planescape monster manual and later incorporated into Forgotten Realms — are an elven Chaotic Good variant of werewolf. Lythari have no hybrid form and "convert" others very rarely — this requires a special ritual and done only when they are really sure they want someone to join their tribe.
"Salient abilities" can make any werewolf (or vampire, golem, mummy, etc) different from any other of its kind. The Van Richten's Guide to Werebeasts gives exhaustive details on all forms of lycanthropy.
The Demiplane of Dread is also home to its own unique variant of werewolves, the Loup-Garou, which are more powerful than "normal" werewolves in 2e.
4th edition D&D makes yet another change. Shifters are presented as playable races in Monster Manual 1 and Player's Handbook 2. Regular werewolves, however, are monsters only... and they no longer transmit the "curse of lycanthropy" upon biting someone, just a generic disease. They also have a Healing Factor that can be suppressed by silver. As of a few recent sourcebooks, players can once again be full werewolves. There are two variants; one allows the player to transform between humanoid and wolf forms at-will, but makes hybrid form a daily power, while the other makes both encounter powers. Or they could just have played a Druid, who can spend most of their time as a wolf if they want.
Exalted: There is absolutely nothing preventing a Lunar Exalt from having a wolf as their spirit-shape, although they're not exactly your average werewolves. As far as official characters go, Ma-Ha-Suchi is Mode Locked into a humanoid goat hybrid form as a result of Wyld-induced Body Horror. He can still assume his human form, wolf form, or any other form he's acquired. But he's ashamed of his horns and hooves in his non-hybrid forms (not to mention that the hybrid form is designed for maximized asskickery).
Blood Bowl: The werewolves who take part in the game are tormented creatures driven into a wild frenzy by their conflicted nature and are prone to outbursts of crazed violence, something that would make them the prefect Blood Bowl player if they could confine such violence to the opposition. As such, werewolves almost exclusively play for Norse Teams (who don't care about such incidents) and Necromantic Horror teams (where any damage they cause to their own side can be easily repaired by the Necromancer Coach).
Mordheim: Balewolves, also called Things in the Woods, are humans affected by a Chaos-induced curse that causes them to transform into monstrous, mutated and feral hound-like beasts with leather-hard skin and a healing factor; their transformation is uncontrolled, and has a chance of happening whenever the bearer is injured. This is transmissible, and humans bit by these beasts risk succumbing to the same curse.
The Werewolf NPC introduced in the Blood Moon expansion functions in a similar fashion to the Grim Reaper, in that it's moved around the board whenever a player rolls a one for their movement and attacks any player character it lands on. This attack can result in the player losing a life, a follower, contracting lycanthropy, or (if the player is lucky) choosing from a list of beneficial effects.
Player characters can contract lycanthropy, which grants them bonuses to their rolls in battle and psychic combat during the night, at the cost of being forced to attack any player character that is in a space that the lycanthrope lands on. Lycanthropy can be cured by the wolf's bane object, among other means.
The Space Wolves' gene-seed contains a specific gene sequence called the Canis Helix which causes animalistic physical changes such as lengthened canines, a heightened sense of smell, and their skin gradually becoming darker and more leathery as they age. However, occasionally these changes go out of control and turn the Space Wolf into a feral monstrosity. This danger is called the Curse of the Wulfen, and each Space Wolf aspirant must confront the Curse as they receive the gene-seed—either their bodies will stabilize so that they become a full Marine, they'll degenerate into a Wulfen, or they'll appear to stabilize only to manifest the Curse in the heat of battle. Wulfen make up the vast majority of the Space Wolves' 13th Company, which disappeared into the Warp millennia ago along with Leman Russ, although the rules supplement Curse of the Wulfen brought the 13th Company back from the Warp to Fenris to help fight off a Chaos invasion.
Warhammer Fantasy: Skin Wolves are people cursed with the blood of a Chaos-mutated wolf. In battle, their wolf form erupts out of their body, still draped in their tattered human skin, and only once their hunger is sated does their form collapse and the human has to tear his way out of the wolf's skin.
An optional werewolf template is an uncontrollable problem triggered by the full moon. They're very hard to kill but curiously don't have any special level of strength like most werewolves.
In the Banestorm setting, people so afflicted turn into actual wolves. It's also not contagious; either you or an ancestor has to have been specifically cursed.
The game's original werewolf creatures are Greater Werewolf from the Homelands set, whose art shows it growing a wolf head from the side of its human face as the full moon shines in the sky; Treacherous Werewolf from Judgement; and Lesser Werewolf from Legends; the latter two are both depicted as wolf men. Unlike later werewolf cards, these are aligned with Black, the color of darkness and traditional horror monsters — later werewolf cards are Red, the color of emotion, chaos and power, and Green, the color of nature and wild beasts.
The werewolves of Innistrad typically resemble humans with hair, wolf heads and tails, and large claws, but most designs have an exaggerated chest and arms to emphasise their power and savagery. They transform at night, with the likelihood of a given werewolf turning increasing as the full moon approaches; few if any werewolves transform during the new moon, while all turn under the full. In-game, this is represented by a turn where nobody casts any spells, with the break of "day" coming when somebody casts two spells in a turn. In-lore, the condition begins when a victim is marked for transformation by a group of werewolves, usually after being bitten or scratched. The werewolf pack in question will howl together in the night, calling the victim to them. Over the course of the night, the victim runs and hunts with the pack, transforming into a full-fledged werewolf as their human essence enters a state of conflict with the essence of the wild. Werewolf groups, called howlpacks, are savage and disorganized affairs and led by their strongest, most savage member, who must continuously defend their position against the others. A couple of unusual varieties also arose from the broader werewolf population during certain major events:
During the events of the Eldritch Moon set, the influence of the Eldrazi Titan Emrakul affects the werewolves alongside all other living things. These werewolves, called the Dronepack, permanently lose their human form, and instead begin to transform into horrific, lupine Animalistic Abominations.
During the events of Innistrad: Midnight Hunt, when Innistrad begins to enter The Night That Never Ends after the moon was used to seal Emrakul, the growing influence of the lengthening night and errant moon cause some werewolves to mutate into the "dire strain", a breed of werewolves who are tall, lanky and grim when human and hulking slabs of Lightning Bruiser muscle when wolf men.
Rifts: In keeping with the Fantasy Kitchen Sink, several varieties of werewolves exist. The Conversion book has several brands of lycanthrope, including werewolves, werejaguars, etc, which are basically creatures that can take on a human or animal appearance. They are essentially aliens, not cursed humans, and can't transmit their lycanthropy to others. Different kinds of werewolves exist in other settings, such as Russia and Canada, based on local folklore. There are also Zenith Moon Warpers, natural shapeshifters who can take on any form but are forced to revert to their true, lupine selves when the moon is at its zenith.
The Rifter: A set of semi-official articles expands the Werebeasts to the Nightbane game. There, Weres form clans collectively known as the Children of the Moon. These clans run the gamut from Corrupt Corporate Executives, mercenaries, seers, insane beasts, superpowered mutants, and their own internal police force. According to their creation legend, humans were originally wereapes, but lost their ability to change to their animal forms due to a curse that also gave the werebeasts their vulnerability to silver.
Werewolves are the archetypal lycanthropes, being hunters in the wilderness and banes of travelers, villagers and farmers. They're humanoids afflicted by an infectious curse, which gives them the ability to shift between humanoid, wolf and Wolf Man forms in exchange for being locked into wolf form during the full moon. They can either natural (born to werewolf parents, and themselves werewolves all their lives) or afflicted (born as a normal humanoid and later afflicted through another werewolf's bite).
Afflicted werewolves have difficulty controlling their transformations, and lose their memory and sense of self during the full moon — they'll rampage as an animal all night and then wake up with no memory of their time spent as a wolf. They can be cured of their condition before their first transformation by eating the toxic wolfsbane plant and surviving the ensuing poisoning.
Natural werewolves are in full control of their shifts and retain their minds and memories during the full moon's change. However, they're prevalently Chaotic Evil and deeply contemptuous of afflicted werewolves, other lycanthropes and non-lycanthropic humanoids, viewing the first two groups as their lessers and the third as prey. They however get along fairly well with winter wolves, a breed of giant, intelligent, evil wolves capable of speech. They usually worship Jezelda, the demon lord of werewolves and the moon. Natural werewolves cannot be turned into non-werewolf humanoids by any means short of magic capable of outright changing a being's species.
Rougarous are wolf men who can turn into true wolves and back to their normal form at will. They're often mistaken for werewolves, as the "normal" form is basically one, but are not actual lycanthropes and deeply hate true werewolves, whom they hunt without mercy.
A variant strain of the virus that turns people into vampires transforms humans into loup-garous, mindless Frazetta men types which get stronger and vicious on a twenty-eight day cycle and can infect people by direct fluid contact — say, by biting or scratching them. However, they don't gain animal traits, beyond the extra hair. Other metahumans (dwarves, elves, orks and trolls) undergo different transformations, but all are marked by increased hair growth and aggression and decreased cognitive powers.
There are also Shapeshifters, as in normal animals of all varieties spontaneously giving birth to magically active stock able to take on human form. Not to mention all the dragons who've learned the ability...
In Terror T.R.A.X: Track of the Werewolf (reviewed by Spoonyone), the werewolves seem to possess few characteristics that separate them from normal humans. They can be killed by ordinary methods, speak clearly, and fight using automatic weapons.
Unknown Armies, shockingly, decides to make werewolves fucking weird. Werewolves are what happens when a demon, which are themselves a bit different to the norm, accidentally possess an animal instead of a human being, and it goes wrong. The animal/demon keeps shifting between being human and animal, and the entire universe adapts its own history to decide they'd been that all along. So you get attacked by a wolf, but by the time you get to the ER, the wounds are now unmistakably tears by human fingernails and teeth. Goddamnit, Unknown Armies.
The Werewolves of Miller's Hollow: The werewolves are regular humans during the day and unstoppable monsters during the night, regardless of moon phases. There is also a race that can apparently transform a second time, getting white fur and a taste for other werewolves.
Werewolf: The Apocalypse: The Player Characters are werewolves, creatures distinct from normal humans and normal wolves, although they probably grew up thinking themselves one or the other. These "Garou" are crusading eco-warriors trying to defend the world from the depredations of evil spirits of corruption and greed (and, to a slightly lesser extent, protect the natural world from regular human encroachment). They can change into a variety of forms at will, their go-to for a fight being a giant humanoid wolf with the build of a gorilla. They frequently interact with the spirit world and travel back and forth between realms often; they also have access to magical powers borrowed from spirits, known as Gifts. Werewolves can breed with either humans or wolves, producing children that resemble their birth species until their first change during adolescence or early adulthood; human-born werewolves are called Homid, and tend to think more like humans, while their wolf-born counterparts are called Lupus, and lean more towards instinct and non-visual senses. To mate with another werewolf is strictly forbidden, but of course it does happen from time to time, the result being a deformed and sterile pariah called a Metis, and born stuck in its berserk war-form until it can control its shapeshifting. Werewolves are characterized by Unstoppable Rage, which is a powerful weapon but also an Achilles' Heel.
Werewolf: The Forsaken is the spiritual sequel to "Apocalypse". As in the previous game, these werewolves are dreamspeaking, spirit-walking shaman types who police the border between the realms and keep spirits from setting up camp in the physical world, for the good of all. This game is called "The Forsaken" because the werewolves, called Uratha, are actually outcasts among their own kind, persecuted by other werewolf tribes as part of a blood feud dating to the beginning of the world. Werewolfery is hereditary, almost all werewolves growing up believing themselves human. Shacking up with your fellow werewolf is still a no-no and the result is a scary creature indeed. In all White Wolf games, silver is the big Kryptonite factor for werewolves. A few magical spells in "The Forsaken" use wolfsbane to rob the Uratha of their shapeshifting power for a time. The game also explains the whole "pass the curse by bite" thing by saying that Uratha can follow signs (e.g., the spirit world looking a bit tumultuous) to know that a new werewolf is about to undergo the First Change; some then bite the prospective changer so that they can always track them by scent, hopefully catching up to them when the Change does happen. The game's second edition does make werewolfism somewhat more contagious. Although a bite can't make someone Uratha, exposure to the Uratha can result in a normal human becoming Wolf-Blooded, which is a condition usually reserved for the blood relatives of werewolves. This exposure can mean surviving a werewolf's bite, getting hit by their Weirdness Censor and shaking it off, or getting exposed to spirit activity.
Yu-Gi-Oh!: Ghostrick Werewolf is a peculiar Ghostrick who usually lives as an ordinary human and only plays pranks on the nights he transforms into a werewolf. He’s always looking forward to the next night with a full moon.
Chaotic Good variant of werewolf. Lythari have no hybrid form and "convert" others very rarely — this requires a special ritual and done only when they are really sure they want someone to join their tribe.
from the Homelands set, whose art shows it growing a wolf head from the side of its human face as the full moon shines in the sky; Treacherous Werewolf