Gabriel

After being created by God, Gabriel dwells in Heaven with Michael, Lucifer and Raphael. But due to Michael and Lucifer's constant bickering, he sacrifices his position on the Host as God's greatest messenger, and retreats to Earth.

Dean and Sam Winchester first encounter him in 2.15 Tall Tales, and they think that he's a type of immortal entity known as a Demi-God, more specifically a Trickster. While posing as the Trickster on Earth, Gabriel frequently went around giving people what he judged to be their 'just desserts' which ironically matched their original crime. After reading in lore that the only way kill one is to stab them with a wooden stake dipped in the blood of one of their victims, Dean and Sam eventually stab him with such a weapon but he survives.

A year later in 3.11 Mystery Spot, the Trickster traps them both in a time loop where Dean dies every Tuesday in different ways, that proves unavoidable by any means. Around the hundredth time of Dean dying, Sam realizes who is responsible for everything and confronts the Trickster. He demands for him to reverse what he's done. He reluctantly obliges. While in the real world, Dean dies again, this time for good. Sam spends six months tracking the Trickster. The Trickster assumes the form of Bobby Singer and lures Sam to him. Upon realizing that its the Trickster, he demands that he resurrects Dean and he eventually agrees.

Upon investigating a case in 5.08 Changing Channels where a women claims that her husband was killed by the Incredible Hulk, they become trapped in an alternate reality of TV Shows. The Trickster appears to tell them they need to"learn to play their roles", referring to the desire of Heaven to see them act as Vessels for Michael and Lucifer. Sam and Dean start to suspect that the Trickster is more than he appears to be, and when they trap him in a ring of burning Holy Oil, he reveals himself to be the Archangel Gabriel. He claims that he "skipped out of Heaven, had a face transplant", possibly referencing his vessel.

In 5.19 Hammer Of The Gods, he helps the Gods and the Winchester brothers. He finally admits that God was right in say that humans are better than angels. He confronts Lucifer and meets his fate when his older brother stabs him with his own Archangel Killing Sword.

In 6.06 You Can't Handle The Truth, Dean thinks that a weapon known as Gabriel's Horn of Truth may be causing the people in a town to speak terrible truths to one another. After being summoned by Dean, Castiel searches the entire town for the weapon, and assures Dean that it's not related to the problem.

Powers and Abilities
Immortality: Gabriel, like all celestial beings, is not subjected to time, aging, or diseases, and doesn't need to breathe, eat, or sleep to sustain himself. Gabriel does, however, like all celestial beings because they're all siblings of one another, age and mature, as he is the fourth oldest angel.

Angeilc Possession: Gabriel, like all celestial beings, requires a human vessel in order to physically interact with humans on Earth, as it is a law that applies for all angelic beings.

Invulnerability: Gabriel, like all archangels, is resistent to any form of harm whatsoever, and can't even be harmed by other beings, unless something angelic is invovled, or if he is fighting another archangel.

Super Strength: Gabriel, like all angels, dramatically increases the strength threashold of his host. Healing Factor: When Gabriel's vessel does get damaged by something angelic, he can heal the wound(s) instantly.
 * Overpowering: Gabriel can easily overpower other angels, lower deities (but not higher ones or God himself), humans, creatures, with his might.

Teleportaion: Gabriel, like all celestial beings, can vanish and reappear anywhere in time, space, and any place on the face of the Earth.

Time Manipulation: Gabriel can easily send himself and others forward or backwords to any point in history.

Telekinesis: Gabriel can move people and or objects just by thinking.

Superhuman Intelligence: Gabriel possesses an immense amount of knowledge of the Universe.

Reality Warping: Gabriel, as a high class celestial being, can warp reality, whether it be by making things appear out of thin air, or by reshaping obejcts into something else entirely, or by creating unreal dimensions and large time loops.

Resurrection: Gabriel, like all archangels, can easily revive dead people.