Shapeshifters can change their form so as to appear as any person living, dead, or fictional. Most must shed their skin, teeth, and nails to change from one form to another. It appears that not all the shapeshifters have the exact same abilities: Dean says that the one they encounter in Milwaukee shifts faster than the one they saw in St. Louis, and the Alpha Shapeshifter - the progenitor of all shapeshifters - can shift almost instaneously without shedding his skin or changing his clothes. They can be identified by a Retinal Flare that shows up when they are filmed. They take on a person's physical appearance and access the thoughts of the person they are mimicking. They can take on a deceased or fictional person's physical appearance from pictures or from film and can have children by impregnating human women. They can be killed with silver through the heart, either a bullet or a blade, iridium or decapitation.
A a shojo (or shojo) is a sea spirit with a fondness for alcohol. It can be harnessed to carry out an individual's desires by use of a spell box. The shojo can only be seen when a person is drunk. They are stronger than humans, have long clawsfor greater attack, kills by disemboweling, are telekinetic and can only be seen when the person is drunk. They can be killed by stabbing with a samuarai sword consecrated by a Shinto blessing.
a siren can change its shape to appear human. It may seem to be either male or female, depending on how it chooses to approach a victim. It can manipulate feelings of love, whether sexual or platonic, and causes its victims to kill someone they love. The siren's call in Supernatural is transmitted through saliva. It first charms its way through the victim's defenses by reading their mind and pretending to be the "perfect person" for the victim. It then infects them by fluid transfer. The infection leaves traces of oxytocin in the victim's blood - this is a love hormone that provokes feelings of euphoria. Its true face can be seen in a mirror and bronze dagger dipped in the blood of some under it's spell will kill it.
Skinwalkers are humans that can make a complete transformation into a canine. The particular breed of canine seems to vary depending on the person. They are similar to werewolves in that they can be killed with silver, they infect others with a bite, and they like to eat the hearts of their victims; however, their mutations are complete and are not limited by the phases of the moon. Like Vampires and more notably, canines, they seem to have a pack mentality. When they are killed in canine form, they revert back to their human form. The Alpha Skinwalker was the very first skinwalker and, although not seen, he directs the actions of numerous packs of skinwalkers. Their main objective seems to be infiltrating families disguised as pets and then biting them at a signal in order to create more skinwalkers. They can alter into their canine form at any time, have a superior sense of smell even in human form and can infect others with a bite so that they become skinwalkers themselves. The can be killed by being peirced through the heart or the head with silver.
A vampire is created when a person ingests vampire blood, but the transformation is not complete until they feed on human blood. Once turned, they suffer from bloodlust and must feed on blood, human or animal, to survive. Unlike folkloric vampires, they do not require an invitation to enter a home and are not killed by sunlight. They also prefer to live in packs in locations called nests, and will mate for life. After death, vampire souls go to Purgatory. The Alpha Vampire was the very first vampire and he appears to have a psychic connection with other vampires. By the year 2006, vampires had been hunted so intensively and become so rare that John Winchester had thought they were extinct but in the year 2010, the Alpha Vampire uses his psychic connection to encourage vampires to feed on blood from blood bags and focus on increasing their numbers. A cure for vampirism exists, but only if the vampire has not yet drunk human blood. They need to drink a mixture that includes the blood of the vampire that turned them. Have extremely enhanced senses that include being able to smell humans and vampires over long distances, and the ability to see in pitch darkness. They can exhibit an eyeshine like effect, have sharp, pointed, retractable teeth that emerge from their gums and extend beyond their human teeth and are immortal and unchanging. They can infect others by feeding them their blood so that they turn into vampires themselves. If they have enough human blood, they can heal quickly from any wound besides amputation. Their weaknesses include sunlight. It's not deadly, but can cause a nasty sunburn. Vampires prefer to sleep during the day. Large quantities of Dead Man's Blood can paralyze a vampire and cause wounds that are slow to heal. Cutting off the head of a vampire will kill it and angels can burn vampires from the inside out with a touch, killing them. A special bullet fired from "the Colt" can kill a vampire. A vampire must feed on blood, human or animal, to survive (it is unknown how long a vampire could survive without feeding before it would starve to death, or if such a thing is even possible). Burning saffron, skunk's cabbage and trillium blocks a vampires scent. There is also Vamptonite, the blood of humans which has been poisoned by the Leviathan food additive is fatal to any vampire who ingests it. This is also effective if the blood is injected directly from a syringe.
A vengeful spirit is one that acts violently to avenge something a wrong done to them. While they are generally Ghosts, the spirit may belong to someone still alive but close to death. This group does not include the spirits of people continuing acts of evil that they perpetrated while alive or those acting for their own ends. Although vengeful spirits can essentially target those who committed crimes against others, their judgements can be warped by their time dead; as an example, a ghost who targets those who kill family members cannot distinguish between brothers who killed their father to collect on his life insurance or a girl whose cousin died in a car accident where she was driving. A vengeful spirit's weaknesses are the same as a ghost. Salt or iron will dispell it or repel it but not kill it. In order to be killed the spirit's bones must be salted and burned. In some cases the spirit might be attached to a physical object, and this willneed to be salted and burned also.
(1) Supernatural Wiki