Wereboars, as their name suggests, are therianthropes of a porcine vareity, being humans with the ability to turn partially or wholly into a wild pig. Despite the masculine title used, female wereboars do exist as well, but they still maintain the characteristic tusks. Now, this idea sounds kind of stupid and... well, we're not going to lie; it kind of is. But wild pigs are actually ferocious and dangerous animals, who will readily kill and eat people; there's a reason that boar hunting was seen as the province of the aristocracy... and also why they used fucking huge spears with secondary prongs along their length - to keep the boar from just impaling itself all the way along the shaft out of sheer desire to murderfuck the bastard who skewered it in the first place.
D&D and PF
Though they aren't technically one of the "core" werebeasts of Dungeons & Dragons - that honor goes to the Werewolf, Wererat and Werebear - wereboars are very close in the second tier, and have a long history. They first debuted way back in the original "White Box" in 1974! From there, they made it into both Basic D&D (in the Basic Set and Rules Cyclopedia) and Advanced Dungeons & Dragons (Monster Manual I for 1e, Monstrous Compendium Volume Two and Monstrous Manual for 2e), the Monster Manual for Dungeons & Dragons 3rd Edition, the Monster Manual 2 for Dungeons & Dragons 4th Edition, and finally the Monster Manual for Dungeons & Dragons 5th Edition... actually, it might be accurate to consider them a primary therianthrope strain.
Wereboars are also found in Pathfinder, appearing in the Bestiary 2.
In D&D, wereboars are portrayed as the surly jerks of the therianthrope strain. Just like werebears are known for being one of the few Good therianthropes, wereboars are formally classed as True Neutral in most editions of D&D - 4th and 5th are the only exceptions so far. In both BECMI and AD&D (3e is just a watered down version of AD&D, wereboars are characterized as sullen, bad-tempered jerks who prefer to isolate themselves in the wilderness; rude, crude and vulgar, even their friends are often the source of much grumbling and complaining, and although they are known to be unflinchingly loyal once their hard-earned friendship is won, it can be difficult to tell when a wereboar is feeling friendly or cantankerous. Sort of like an extra-grumpy dwarf.
Another dwarf-like trait is their deep familial love; irascible and obnoxious as they are, wereboar families are close-knit. This might have to do with how many of them there are; female wereboars birth 1d4+2 offspring per pregnancy, producing seemingly human children who, although very small by human standards, are strong and tough, able to crawl within hours of being born. These kids age quickly, gaining the ability to assume their alternative forms at adolescence, which they reach at the age of 8 years old. A wereboar father appears to be distant and aloof, but is actually a staunch protector who will attack any foe who threatens his family, no matter how uneven the odds. Females are even more aggressive when defending their young, and both parents are utterly fearless in their protection
Similarly to werebears, the wereboar typically lives in a cave or a cabin in dense woodland, ideally far away from towns or cities. Unlike a werebear, a wereboar's home is usually a dump - cabins are ramshackle affairs, and both kinds of lair are ill-kept. Slovenly by nature, wereboars believe in using something until it's broken and then replacing it rather than expending the effort to care for it. A wereboar's lair is typically home to a primitive garden - a field cleared by grubbing around in the dirt as a boar, then strewn haphazardly with a variety of seeds and bulbs in the hope that something edible will subsequently grow. They feed on a mixture of small game, vegetables and fungi, but their cooking leaves much to be desired; half-burned meat and coarse stews tends to be the limit of their culinary skill. Wereboars are known for their love of truffles, and have an unparalleled ability to sniff them out - even in their human form, a wereboar can find truffles hidden several feet underground.
Wereboars are isolationists, distrusting pretty much everybody as a potential threat; they don't even like normal hogs. This is why they tend to attack other races who encounter them, especially if they are stumbled across in hog form. Weirdly, they apparently get along with orcs and half-orcs pretty well, and are known to assist or ally with orcs. This trait of allying with orcs is retained in 5th edition, and is the only apparent excuse given for portraying them as Neutral Evil instead of the traditional Always Neutral.
In the World Axis, wereboars are... well, we don't actually know much because they only appeared in the MM2 and so didn't get much fluff. They are still jerks, but are less anti-civilization than their counterparts from the Great Wheel; these wereboars are provocateurs who like to hang out in rough taverns or on the streets so they can pick fights with people.
On Mystara, wereboars are... pretty much identical to the standard wereboars here. However, they compete with another, more malevolent strain of porcine therianthrope in the wereswine. The two races despise each other, and will kill (and eat) each other whenever they can. One unique trick they have is the ability to create violent earth tremors by stomping their hooves, which can potentially knock opponents off of their feet.
Like most of the therianthropes, wereboars have had a few abortive attempts at being PC-friendly given to them. They appeared twice in Dragon Magazine; first as a race for Advanced Dungeons & Dragons 1e in issue #24, and then as a creature class in issue #313. In BECMI, wereboars are a race-class in PC4: The Night Howlers.
World of Darkness
One of the lost types of Fera, the Grondr were a type of Wereboar that specialised in hunting and cutting off Wyrm taint from the source; whilst the Gurahl healed the damage the Wyrm did, these would be the fuckers charging in headfirst and eating away at the taint. Unfortunately, the Garou didn't like that there was another breed that threatened their chance to be top-dog Wyrm slayers, so they decided to genocide them, saying that the taint they ate had affected them, and turned them evil (which was complete bullshit).
And so their Kinfolk were hunted down and killed, leaving them essentially extinct. The remnants of their kinfolk ironically became the Wyrm-Tainted Skull Pigs, playing into what the Garou had hinted them for. The Grondr, whilst alive, were known for being proud and headstrong, and it was only after they were gone the Garou real sowed how they had fucked up.
- Oinkbane - A /tg/ creation and known as one of the most proficient wereboar assassins in all the land. Known for his completely unconventional tactics that are too subtle for mortal minds to comprehend.